R34 calculated directly in MAD is very large, about 700 m, therefore threshold is very small.
However, calculation of R34 from the betas and phase advance gives a more sensible value of about 17 m (threshold of about 10 mA). But of course, these numbers should be the same.
Perhaps there is a bug in both MAD and MLC in the calculation of the vertical dispersion, such that errors could be propagated and grow. Need to check this!!!
Tuesday, July 03, 2007
Thursday, June 07, 2007
Beam Loss notes
Beam loss/collimation issues on 4GLS:
1. Parasitic loss should be localised deliberately rather than randomly - so we know where it's going. This appears to be the philosophy of the APS ERL proposal, and the Japanese ERL proposal. http://www.erl07.dl.ac.uk/Tuesday_Presentations/WG_2/Session_1/Xiao-ERL07-3.pdf
although admittedly they are using fewer collimators; but their beam power is about 10x greater (700 MW cf our 55 MW).
Also see:
http://www.aps.anl.gov/News/Conferences/2006/APS_Upgrade/apsmac/Borland_ERLPhysics.pdf
Japanese ERL proposal thinks about localisation too:
http://epaper.kek.jp/fls06/TALKS/WG221_TALK.PDF
but one of the things they are thinking about is trapping of very small losses (in the few Watt level) from gas scattering.
So I think that localisation is a sensible way to go. The collimator length does not depend much on the total power - the collimator lengths is just there to stop the shower coming out the end of the collimator with too high a mean energy. 200 mm Cu is the estimate for 550-750 MeV incident electrons.
2. We are worried about irradiating the undulators, and we have a lot of those. This is what XFEL worry about:
http://flash.desy.de/sites/site_vuvfel/content/e403/e1642/e1849/e1933/infoboxContent2164/TESLA-FEL-2007-051.pdf
(this is a very detailed paper that I have not digested yet!)
But I think at the moment that it is similar in principle to the BESSY-FEL collimation design:
http://web.elettra.trieste.it/fel2004/proceedings/papers/TUPOS02/TUPOS02.PDF
Remember that the beam power in the FELs is much lower than our 55 MW, so we should be as worried about collimation as they are!
3. At the moment, we don't know the best way to detect beam loss. Some issues:
a. Measurement of differential current monitors on the primary beam - I don't think this will be nearly good enough. The S/N isn't good enough - differential measurements are good enough for 'catastrophic' loss over ms, say, but not for ongoing losses.
b. Direct measurement of the loss, via scintillation or other techniques seems like the way to go. e.g. cable-based monitors like those used on ERLP. My favourite at the moment is a 'halo monitor':
c. Measurement of pressure rise sounds good (because it's cheap, and doesn't introduce extra components into the vacuum envelope that cause impedance), but I worry about the timescale of response of things like this, and what happens when they aren't working properly - we have lots of experience of that on the SRS!
d. Similarly, measurements of temperature rise are also not great, because you could for example get a mis-tuning of the beam optics which caused localised beam loss, and then not know about it until it was too late.
For all those reasons, I'm still in favour of collimators that will passively protect the other apertures as much as possible, hence have a fairly dense layout of them (regular spacing in phas advance), and to put monitors in as well.
1. Parasitic loss should be localised deliberately rather than randomly - so we know where it's going. This appears to be the philosophy of the APS ERL proposal, and the Japanese ERL proposal. http://www.erl07.dl.ac.uk/Tuesday_Presentations/WG_2/Session_1/Xiao-ERL07-3.pdf
although admittedly they are using fewer collimators; but their beam power is about 10x greater (700 MW cf our 55 MW).
Also see:
http://www.aps.anl.gov/News/Conferences/2006/APS_Upgrade/apsmac/Borland_ERLPhysics.pdf
Japanese ERL proposal thinks about localisation too:
http://epaper.kek.jp/fls06/TALKS/WG221_TALK.PDF
but one of the things they are thinking about is trapping of very small losses (in the few Watt level) from gas scattering.
So I think that localisation is a sensible way to go. The collimator length does not depend much on the total power - the collimator lengths is just there to stop the shower coming out the end of the collimator with too high a mean energy. 200 mm Cu is the estimate for 550-750 MeV incident electrons.
2. We are worried about irradiating the undulators, and we have a lot of those. This is what XFEL worry about:
http://flash.desy.de/sites/site_vuvfel/content/e403/e1642/e1849/e1933/infoboxContent2164/TESLA-FEL-2007-051.pdf
(this is a very detailed paper that I have not digested yet!)
But I think at the moment that it is similar in principle to the BESSY-FEL collimation design:
http://web.elettra.trieste.it/fel2004/proceedings/papers/TUPOS02/TUPOS02.PDF
Remember that the beam power in the FELs is much lower than our 55 MW, so we should be as worried about collimation as they are!
3. At the moment, we don't know the best way to detect beam loss. Some issues:
a. Measurement of differential current monitors on the primary beam - I don't think this will be nearly good enough. The S/N isn't good enough - differential measurements are good enough for 'catastrophic' loss over ms, say, but not for ongoing losses.
b. Direct measurement of the loss, via scintillation or other techniques seems like the way to go. e.g. cable-based monitors like those used on ERLP. My favourite at the moment is a 'halo monitor':
c. Measurement of pressure rise sounds good (because it's cheap, and doesn't introduce extra components into the vacuum envelope that cause impedance), but I worry about the timescale of response of things like this, and what happens when they aren't working properly - we have lots of experience of that on the SRS!
d. Similarly, measurements of temperature rise are also not great, because you could for example get a mis-tuning of the beam optics which caused localised beam loss, and then not know about it until it was too late.
For all those reasons, I'm still in favour of collimators that will passively protect the other apertures as much as possible, hence have a fairly dense layout of them (regular spacing in phas advance), and to put monitors in as well.
Friday, June 01, 2007
4GLS Phasing Options
Phase 1
Would be low current (good for focus on dynamics expts) and retain some of the combined sources vision. Included is the XUV FEL, the far IR FEL and the spontaneous loop (populated to some level).
There was consensus that completing the HAC loop is a good idea. There are good technical reasons for this relating to the RF. I think it also looks good from a general-project-stance consistency point of view.
Low current in Phase 1 means that fewer IOTs and a smaller cryoplant is needed. Feeling was that we'd buy the rating of IOT and PSUs needed for whole project and use one to power several cavities. When we move to higher power buy more of the units.
A move from three injectors to two injectors was proposed as the spec of the HACL system would cover the requirements of the IR FEL system.
The IR FEL beam would be taken off after Module 1 of the main linac. Need either to schedule operation of spontaneous loop and Far IR FEL at different times or use a kicker of some sort (not felt to be tricky at rep rates condidering).
A move from two upstream arcs to one upstream arc was proposed. There's then a requirement to split the XUV-FEL beam from the HACL beam. At the lower rep rates proposed in Phase 1 this is technically feasble with current technology.
Could phase the development of the XUV FEL, e.g. 6/8-40eV first and then 35-100eV. Might not need to do this.
For the discussion the current in the spontaneous loop was 0.3 mA (4.3MHz at 77pC). There was no real discussion of 13MHz at 200 pC (which of course gives 2.6 mA).
I've tried to capture some of the machine implications on the attached powerpoint file. I've not messed with the HACL though.
Phase 2
Would be high current in the spontaneous loop, the VUV FEL, further IR FEL development, further population of the spontaneous sources.
Need to mesh R&D roadmap with injector development.
More IOTs needed and cryo plant needs uprating.
R&D development on kickers permits a single upstream arc and kicker otherwise a second upstream arc needed. Again need to mesh with the R&D roadmap.
VUV FEL incorporated.
Need a set of milestones for eventual delivery of 100mA
Lia will be producing a document on the global view of R&D needed for ERLs with timeline as an output of ERL07.
Clearly the costing matrix would need to capture phasing of the RF and cryo, have the costs for XUV FELs separate, have the cost for the FAR IR photoinjector and FELs separate.
Hope this is clear, it's not that easy to summarise!
Would be low current (good for focus on dynamics expts) and retain some of the combined sources vision. Included is the XUV FEL, the far IR FEL and the spontaneous loop (populated to some level).
There was consensus that completing the HAC loop is a good idea. There are good technical reasons for this relating to the RF. I think it also looks good from a general-project-stance consistency point of view.
Low current in Phase 1 means that fewer IOTs and a smaller cryoplant is needed. Feeling was that we'd buy the rating of IOT and PSUs needed for whole project and use one to power several cavities. When we move to higher power buy more of the units.
A move from three injectors to two injectors was proposed as the spec of the HACL system would cover the requirements of the IR FEL system.
The IR FEL beam would be taken off after Module 1 of the main linac. Need either to schedule operation of spontaneous loop and Far IR FEL at different times or use a kicker of some sort (not felt to be tricky at rep rates condidering).
A move from two upstream arcs to one upstream arc was proposed. There's then a requirement to split the XUV-FEL beam from the HACL beam. At the lower rep rates proposed in Phase 1 this is technically feasble with current technology.
Could phase the development of the XUV FEL, e.g. 6/8-40eV first and then 35-100eV. Might not need to do this.
For the discussion the current in the spontaneous loop was 0.3 mA (4.3MHz at 77pC). There was no real discussion of 13MHz at 200 pC (which of course gives 2.6 mA).
I've tried to capture some of the machine implications on the attached powerpoint file. I've not messed with the HACL though.
Phase 2
Would be high current in the spontaneous loop, the VUV FEL, further IR FEL development, further population of the spontaneous sources.
Need to mesh R&D roadmap with injector development.
More IOTs needed and cryo plant needs uprating.
R&D development on kickers permits a single upstream arc and kicker otherwise a second upstream arc needed. Again need to mesh with the R&D roadmap.
VUV FEL incorporated.
Need a set of milestones for eventual delivery of 100mA
Lia will be producing a document on the global view of R&D needed for ERLs with timeline as an output of ERL07.
Clearly the costing matrix would need to capture phasing of the RF and cryo, have the costs for XUV FELs separate, have the cost for the FAR IR photoinjector and FELs separate.
Hope this is clear, it's not that easy to summarise!
Tuesday, May 22, 2007
ERL07 WG2 Session 2 - Notes
Sakanaka - Ion Trapping
Use kicker to kick out parts of the injector beam - needs fast kicker (1.3 GHz bunch separation), and get ringing. Maybe can avoid ringing by using two kickers Pi out of phase.
Methods to avoid trapping:
1. Gaps - match beam loading in main linac, and use feed-forward RF in injector
2. Beam blow-up - no beam loading in injector, but the fact there is still focusing term from the blown-up bunches mean that the effect on clearing is less good.
3. Moving the beam - 'beam shaking'. Not viewed as a good thing - tends to hits resonances .
Nakamura -Resistive-Wall Beam Breakup
PRST-AB 7, 034402 (2004)
Transverse wakefield can give break-up.
Use kicker to kick out parts of the injector beam - needs fast kicker (1.3 GHz bunch separation), and get ringing. Maybe can avoid ringing by using two kickers Pi out of phase.
Methods to avoid trapping:
1. Gaps - match beam loading in main linac, and use feed-forward RF in injector
2. Beam blow-up - no beam loading in injector, but the fact there is still focusing term from the blown-up bunches mean that the effect on clearing is less good.
3. Moving the beam - 'beam shaking'. Not viewed as a good thing - tends to hits resonances .
Nakamura -Resistive-Wall Beam Breakup
PRST-AB 7, 034402 (2004)
Transverse wakefield can give break-up.
ERL 07 Workshop Notes - Session 1
Michael Borland - Touschek Scattering
Beam-loss mechanisms fall into two classes:
1. Low-energy, unpredictable - collimate at low energy
2. Calculable, e.g. Touschek and Nonlinear Optics
Touschek dominates CW beam loss in low emittance rings. Probably then significant in ERL light source. Touschek is well-studied in rings, but not studied in single-pass accelerators.
Assume gas scattering is smaller than Touschek - at about 1 nTorr.
ERL electron cooler - 5 nC per bunch, 4 um emittance (100 ps bunch length). ERL beam cools both directions. 54 MeV bunches travel 100 m down ERL cooling line - some space charge acting. Will compensate space charge using weak solenoids every 10 m.
3rd-harmonic cavity is used to flatten energy gain of the very long (100 ps) bunch so that energy spread is small enough (4.10^-4 rather than few 10^-3 without 3rd-harmonic)
BBU threshold is high with the small number of cavities and modelled HOMs.
Have a dog-leg which moves the beam H and V at the same time (5 quads for dispersion matching). No perceived issue with space charge at the centre of the dog-leg quad.
300 m turnaround for the beam path.
Accumulation of ions will be only in the turnaround - the cooling region has a big ion beam which will repel the ions in that 100m section.
Path length correction is mechanical - move the arc.
Amplitude stability is 10^-4 in RF - should be good enough.
Beam-loss mechanisms fall into two classes:
1. Low-energy, unpredictable - collimate at low energy
2. Calculable, e.g. Touschek and Nonlinear Optics
Touschek dominates CW beam loss in low emittance rings. Probably then significant in ERL light source. Touschek is well-studied in rings, but not studied in single-pass accelerators.
Assume gas scattering is smaller than Touschek - at about 1 nTorr.
ERL electron cooler - 5 nC per bunch, 4 um emittance (100 ps bunch length). ERL beam cools both directions. 54 MeV bunches travel 100 m down ERL cooling line - some space charge acting. Will compensate space charge using weak solenoids every 10 m.
3rd-harmonic cavity is used to flatten energy gain of the very long (100 ps) bunch so that energy spread is small enough (4.10^-4 rather than few 10^-3 without 3rd-harmonic)
BBU threshold is high with the small number of cavities and modelled HOMs.
Have a dog-leg which moves the beam H and V at the same time (5 quads for dispersion matching). No perceived issue with space charge at the centre of the dog-leg quad.
300 m turnaround for the beam path.
Accumulation of ions will be only in the turnaround - the cooling region has a big ion beam which will repel the ions in that 100m section.
Path length correction is mechanical - move the arc.
Amplitude stability is 10^-4 in RF - should be good enough.
Monday, May 14, 2007
4GLS Diagnostics Discussion Meeting, 14th May 2007
CDR design has obviously changed, but the diagnostic principles haven't changed. The
HACL Gun:
Gun energy - temp diagnostics line
Gun emittance - temp diagnostics line
Cathode emitted bunch length
Issues of run-up from low current to high current
(separate meeting!)
Assume built gun (check Cornell prototype): current measurements, beam centroid measurements, beam profile measurements, insertable screen/Fcup?
Interlocking issue - make sure screens don't go in at high current.
HACL Injector:
Output energy, chirp, bunch length - phase/voltage measurement of each cavity
Tranverse phase space measurement? May be a 'wish-list item.
Boris/Rob/Julian/Hywel to look at essential measurements
XUV Injector:
Collaboration with PITZ?
Fast amplitude stabilisation of RF amplitude and phase during 20 us RF pulse in XUV injector.
Output energy, chirp, bunch length - phase/voltage measurement of each cavity
Tranverse phase space measurement? May be a 'wish-list' item.
Include BC1 setup
Main Linac:
HACL team - measurements list: (Hywel)/Bruno/Rob/Alex
Need to think about the modes we will be running in:
XUV only: 1nC at 1kHz
HACL only: low current/high current/
XUV/HACL only:
Transfer matrix measurements - are they needed?
Energy Recovery/Dump
Measurement of energy recovery efficiency. Measurement of loss at level required?
HACL and IDs
Modes for commissioning again.
Profile monitors - low current with screens only, high current with alternative monitor - are they needed?
Tomography measurement - SR output resolution vs. resolution of other instruments for measuring of transverse profile, e.g. wavelength, diffraction etc.,
THz measurement in straight 1?
Streak cameras at short bunch length - 100 fs resolution under development, 10 fs
EO does not work at high current, use streak cameras at high current in upstream regions of the HACL ID arc.
How do we get the VUV-FEL to work? Bunch length, time overlap,
Discussion: Hywel/Frances/Neil
XUV-FEL
Emittance measurement is under control (Bruno!)
Seed laser diagnostics
Discussion
Neil/Steve/Frances/Bruno/Brian Sheehy/Graeme
IR-FEL:
Establish group: Boris/Bruno/Neil
HACL Gun:
Gun energy - temp diagnostics line
Gun emittance - temp diagnostics line
Cathode emitted bunch length
Issues of run-up from low current to high current
(separate meeting!)
Assume built gun (check Cornell prototype): current measurements, beam centroid measurements, beam profile measurements, insertable screen/Fcup?
Interlocking issue - make sure screens don't go in at high current.
HACL Injector:
Output energy, chirp, bunch length - phase/voltage measurement of each cavity
Tranverse phase space measurement? May be a 'wish-list item.
Boris/Rob/Julian/Hywel to look at essential measurements
XUV Injector:
Collaboration with PITZ?
Fast amplitude stabilisation of RF amplitude and phase during 20 us RF pulse in XUV injector.
Output energy, chirp, bunch length - phase/voltage measurement of each cavity
Tranverse phase space measurement? May be a 'wish-list' item.
Include BC1 setup
Main Linac:
HACL team - measurements list: (Hywel)/Bruno/Rob/Alex
Need to think about the modes we will be running in:
XUV only: 1nC at 1kHz
HACL only: low current/high current/
XUV/HACL only:
Transfer matrix measurements - are they needed?
Energy Recovery/Dump
Measurement of energy recovery efficiency. Measurement of loss at level required?
HACL and IDs
Modes for commissioning again.
Profile monitors - low current with screens only, high current with alternative monitor - are they needed?
Tomography measurement - SR output resolution vs. resolution of other instruments for measuring of transverse profile, e.g. wavelength, diffraction etc.,
THz measurement in straight 1?
Streak cameras at short bunch length - 100 fs resolution under development, 10 fs
EO does not work at high current, use streak cameras at high current in upstream regions of the HACL ID arc.
How do we get the VUV-FEL to work? Bunch length, time overlap,
Discussion: Hywel/Frances/Neil
XUV-FEL
Emittance measurement is under control (Bruno!)
Seed laser diagnostics
Discussion
Neil/Steve/Frances/Bruno/Brian Sheehy/Graeme
IR-FEL:
Establish group: Boris/Bruno/Neil
Friday, May 04, 2007
4GLS Beam Loss initial brainstorm - 4th May 2007
Machine protection system has to be designed - we need to consider all likely eventualities.
General considerations: some diagnostics will cause loss (e.g. running into an FCup), so we will need different operating modes to allow this.
As with other facilities, we will need an interlock system
We need to obtain a time constant for the cryomodules - how long will they ring if the power goes off? About 0.1ms
Machine protection scales:
30-300 ns is as fast as signals can travel through the 4GLS; machine protection can't go as fast as this.
Typical switch off in machine protection is 10s of us (check).
Vacuum faults:
Slow leak - Gas bremsstrahlung (radiation monitors), ion trapping change (how much?), linac ices up,
Fast leak - triggers gate valve - need to turn off electrons before valve shuts. What happens if a gate valve shuts by itself? This is probably standard accelerator technology, but the beam power is very high in our case. e.g. 5 kJ can hit a faulty valve in 0.1 ms if the electrons are not turned off! Same goes for diagnostics, e.g. screens.
HACL:
Cathode:
Long time constant change (QE change)
Laser shut-off - probably not a problem as there are no electrons
Laser loses sync with RF system (outside bucket) - bunch is at different phase, so is bunched differently and comes out with different energy from injector. How fast can that happen?
VUV-FEL mode: low rep rate selected. Can the laser go CW (chopper fails)? How will the chopper work?
other failure modes of the laser/cathode?
Gun:
HV PSU trip-off (low SF6, PS fault) - injector energy will reduce over a time until we can trip off the laser. Particles will go in the wrong direction in BC1 - need to collimate?
HV PSU set wrong - what happens if we are mis-tuned, and how do protect against it?
Buncher:
Fails, beam is not bunched - what happens? Energy spread and length growth - will this be beyond
Buncher works at the wrong phase? Can the acceleration produced be significant
HACL Modules:
Modules at wrong phase
Wrong voltage - probably be to reduce the voltage
Everything here has a time constant
RF control fault - e.g. missing bunches or pulses - gives transient beam-loading
BTS:
Magnet failure:
Wrong setting/Trip - may for example have to arrange that inductance of magnets is high to make their intrinsic turn-off slow. May get this for free...
Some magnets are more critical than others (e.g. the ones upstream of the main linac)
Collimators are in the HACL arcs to take a short pulse of errant beam, and also to catch halo; main linac can easily change in 0.1ms.
Magnet failure can cause path length change - need to check how big this change can be.
Magnet failure can cause beam movement which can hit the IDs - need to do something similar to what we did for the SRS and DIAMOND, e.g. ray-tracing of possible beam routes through the IDs.
Main Linac:
Check - ILC linac failure modes.
VUV-FEL:
Lasing goes on and off - should be no problem as unlased energy range lies within lased energy range.
Steering from misaligned/faulty magnet arrays - can't go too fast, should be able to be
PLC:
PLC moves or there is a magnet failure - energy recovery is lost. Linac will pick this up.
Dump:
Energy too high - power load too high, irradiation. Beam can also hit crotch and spreader.
Energy too low - absorption depth in dump will be less.
Raster magnets fail - need to independently sense the raster scan failure, as there will be lots of radiation/signal in this part of the machine.
XUV-FEL:
Gun/Injector:
Missed pulses can occur - probably doesn't matter if there are no pulses, e.g. in main linac.
Overpulses (e.g. extra laser pulses) - then get extra electrons that are not being accelerated. Depends on the length of the RF pulse.
Linac:
Wrong relative phase of XUV and HACL bunches. Can the HACL bunches 'push' the linac phase around enough to change the XUV gun phase.
HHG laser can melt something directly?
General considerations: some diagnostics will cause loss (e.g. running into an FCup), so we will need different operating modes to allow this.
As with other facilities, we will need an interlock system
We need to obtain a time constant for the cryomodules - how long will they ring if the power goes off? About 0.1ms
Machine protection scales:
30-300 ns is as fast as signals can travel through the 4GLS; machine protection can't go as fast as this.
Typical switch off in machine protection is 10s of us (check).
Vacuum faults:
Slow leak - Gas bremsstrahlung (radiation monitors), ion trapping change (how much?), linac ices up,
Fast leak - triggers gate valve - need to turn off electrons before valve shuts. What happens if a gate valve shuts by itself? This is probably standard accelerator technology, but the beam power is very high in our case. e.g. 5 kJ can hit a faulty valve in 0.1 ms if the electrons are not turned off! Same goes for diagnostics, e.g. screens.
HACL:
Cathode:
Long time constant change (QE change)
Laser shut-off - probably not a problem as there are no electrons
Laser loses sync with RF system (outside bucket) - bunch is at different phase, so is bunched differently and comes out with different energy from injector. How fast can that happen?
VUV-FEL mode: low rep rate selected. Can the laser go CW (chopper fails)? How will the chopper work?
other failure modes of the laser/cathode?
Gun:
HV PSU trip-off (low SF6, PS fault) - injector energy will reduce over a time until we can trip off the laser. Particles will go in the wrong direction in BC1 - need to collimate?
HV PSU set wrong - what happens if we are mis-tuned, and how do protect against it?
Buncher:
Fails, beam is not bunched - what happens? Energy spread and length growth - will this be beyond
Buncher works at the wrong phase? Can the acceleration produced be significant
HACL Modules:
Modules at wrong phase
Wrong voltage - probably be to reduce the voltage
Everything here has a time constant
RF control fault - e.g. missing bunches or pulses - gives transient beam-loading
BTS:
Magnet failure:
Wrong setting/Trip - may for example have to arrange that inductance of magnets is high to make their intrinsic turn-off slow. May get this for free...
Some magnets are more critical than others (e.g. the ones upstream of the main linac)
Collimators are in the HACL arcs to take a short pulse of errant beam, and also to catch halo; main linac can easily change in 0.1ms.
Magnet failure can cause path length change - need to check how big this change can be.
Magnet failure can cause beam movement which can hit the IDs - need to do something similar to what we did for the SRS and DIAMOND, e.g. ray-tracing of possible beam routes through the IDs.
Main Linac:
Check - ILC linac failure modes.
VUV-FEL:
Lasing goes on and off - should be no problem as unlased energy range lies within lased energy range.
Steering from misaligned/faulty magnet arrays - can't go too fast, should be able to be
PLC:
PLC moves or there is a magnet failure - energy recovery is lost. Linac will pick this up.
Dump:
Energy too high - power load too high, irradiation. Beam can also hit crotch and spreader.
Energy too low - absorption depth in dump will be less.
Raster magnets fail - need to independently sense the raster scan failure, as there will be lots of radiation/signal in this part of the machine.
XUV-FEL:
Gun/Injector:
Missed pulses can occur - probably doesn't matter if there are no pulses, e.g. in main linac.
Overpulses (e.g. extra laser pulses) - then get extra electrons that are not being accelerated. Depends on the length of the RF pulse.
Linac:
Wrong relative phase of XUV and HACL bunches. Can the HACL bunches 'push' the linac phase around enough to change the XUV gun phase.
HHG laser can melt something directly?
Tuesday, May 01, 2007
Friday, April 27, 2007
CICT/CI/ASTeC Support Meeting, 27th April 2007
Notes and Actions:
1. IT Services
PC Support is now called DL IT Support - now in Canal View
No longer particular support hours. Emails now going to Footprints helpdesk support.
New support address: dlitsupport'at'dl.ac.uk
New support website: http://itservices.dl.ac.uk/ - an excellent step forward.
3rd-party access forms - have been updated on the website for now. Some changes will be made, and a web form will be made.
Campus IT may be put out to tender (bad idea). DL would like to do it.
2. Outgoing CI email addresses. Can be done (e.g. Swapan's email address), but will be done on an individual-by-individual basis on request.
3. PPD files - to go onto IT support website http://itservices.dl.ac.uk/printing/printing3.htm. Chris and Hywel to list out printers post-meeting.
4. POPmail instructions. These work, and will be put onto the IT Services website.
5. Backups - We have bought 2 legato licenses. They haven't arrived yet.
6. apsv5 still not working - C.Dean still looking at it. The machine may have to be sent back to Dell.
7. New CI website - Barbara Runcie will be the webmaster.
Design produced in a couple of weeks.
Agree design with Swapan.
Migrate existing content to new design (Barbara/Stuart)
Migrate to Rythmix and updates done by Barbara. Updates by e.g. Liz to be explored.
8. ASTeC/CI website interaction - meeting with Swapan and Mike P. to find out what they want. (Action HLO)
9. C.Dean to upgrade Plone version projects.astec.ac.uk/ (lowish priority).
1. IT Services
PC Support is now called DL IT Support - now in Canal View
No longer particular support hours. Emails now going to Footprints helpdesk support.
New support address: dlitsupport'at'dl.ac.uk
New support website: http://itservices.dl.ac.uk/ - an excellent step forward.
3rd-party access forms - have been updated on the website for now. Some changes will be made, and a web form will be made.
Campus IT may be put out to tender (bad idea). DL would like to do it.
2. Outgoing CI email addresses. Can be done (e.g. Swapan's email address), but will be done on an individual-by-individual basis on request.
3. PPD files - to go onto IT support website http://itservices.dl.ac.uk/printing/printing3.htm. Chris and Hywel to list out printers post-meeting.
4. POPmail instructions. These work, and will be put onto the IT Services website.
5. Backups - We have bought 2 legato licenses. They haven't arrived yet.
6. apsv5 still not working - C.Dean still looking at it. The machine may have to be sent back to Dell.
7. New CI website - Barbara Runcie will be the webmaster.
Design produced in a couple of weeks.
Agree design with Swapan.
Migrate existing content to new design (Barbara/Stuart)
Migrate to Rythmix and updates done by Barbara. Updates by e.g. Liz to be explored.
8. ASTeC/CI website interaction - meeting with Swapan and Mike P. to find out what they want. (Action HLO)
9. C.Dean to upgrade Plone version projects.astec.ac.uk/ (lowish priority).
Thursday, April 26, 2007
Seminar 26th April - Sergiy Khodyachykh, PITZ Diagnostics
Tomography uses MENT algorithm (Maximum ENTropy) to reconstruct the phase space in a 4-screen FODO channel.
David Holland Seminars - Pump Probe Techniques, 24/26th April 2007
Questions:
Multiple pumps per probe/probes per pump?
Relative size of pulse vs. delay? pulse much less than delay
As well as observing a reaction, there is the possibility of active control by using short pulses to affect the outcome of a chemical reaction.
Frequency control - Brumer-Shapiro
The interference between two degenerate pathways. Analogous to affecting the interference in Young's slits experiments.
http://prola.aps.org/abstract/PRL/v79/i21/p4108_1
Time-domain control - Tannor-Rice
Wavepacket control (pump-dump scheme)
Chem. Phys. Lett. 262 362 (1996)
Chem. Rev. 104 1813 (2004)
Shaping the light pulse allows clever control of the optical pulse to give greater control of the chemical reaction. - Question: how does this depend on variations in the input light pulse? e.g. a varying electron bunch will produce a varying photon pulse, which will change the resulting shaped pulse. This must be some sort of limitation.
26th April:
There is a limit to the repetition rate that can be used on the VUV-FEL which arises from the limit rate of time-of-flight detectors. This places a limit of around 10s of kHz for certain types of experiment.
Multiple pumps per probe/probes per pump?
Relative size of pulse vs. delay? pulse much less than delay
As well as observing a reaction, there is the possibility of active control by using short pulses to affect the outcome of a chemical reaction.
Frequency control - Brumer-Shapiro
The interference between two degenerate pathways. Analogous to affecting the interference in Young's slits experiments.
http://prola.aps.org/abstract/PRL/v79/i21/p4108_1
Time-domain control - Tannor-Rice
Wavepacket control (pump-dump scheme)
Chem. Phys. Lett. 262 362 (1996)
Chem. Rev. 104 1813 (2004)
Shaping the light pulse allows clever control of the optical pulse to give greater control of the chemical reaction. - Question: how does this depend on variations in the input light pulse? e.g. a varying electron bunch will produce a varying photon pulse, which will change the resulting shaped pulse. This must be some sort of limitation.
26th April:
There is a limit to the repetition rate that can be used on the VUV-FEL which arises from the limit rate of time-of-flight detectors. This places a limit of around 10s of kHz for certain types of experiment.
Seminar 26th April - John Singleton, BigLight
Tallahassee, NHMFL - National High Magnetic Field Laboratory
3 sites in the USA
3 FELs - NIR, MIR, FIR. NIR could operate simultaneously with MIR, but maybe with less power. NIR is upstream of MIR. Swept-frequency operation would be difficult, but there is not much demand, so will just do spot measurements
Coherent Undulator for Terahertz Spectroscopy (CUFT)
Draft design of light source overseen by George Neil.
USD2.5M
1. Design of user facility ('co-location')
2. Research into pulse manipulation using electrostatic accelerator
Parameters:
Injector/dump 10 MeV - thermionic gun
Linac 60 MeV
1m to 1mm wavelengths, plus THz
3 or 4 wigglers - rapid tunability, well-defined polarisation states
Current? 1mA, peak 45A
Bunch repetition rate? Variable bunch trains. 0.5 to 20 ps bunch length, 11.8 MHz repetition rate either pulsed or CW, 0.3% energy spread
1.3 GHZ RF
Emittance 20 mm-mrad
10-20 fs timing jitter - how is it used? (ask George Neil)
NIR lt 60 MeV 1.6 kW
MIR lt 30 MeV 700 W (will actually be 60 MeV because FELs using same electron bunches simultaneously)
FIR 7-10 MeV 300W
Interest is in use of FEL light in combination with high magnetic fields. Fields up to 180 Tesla available at LANL!! (pulsed)
LANL - 65/90 T pulsed fields available to users.
FSU site - 45 T DC field available to users (wow). 2 more magnets 25-30 T and 36 T (so-called series connected design which makes operation and interlocks simpler).
(need to watch out where you site the accelerator, and use passive shielding to reduce the stray fields from the DC magnets).
Experimental need - 1ps, pump-probe, THz to near-IR.
Timeline (hoped)
2008 funding (NSF only) - about 25-30M (not including staff or building)
2012 completion
Detail design - 2008/2009 (15 staff-years).
Make some of it? (injector for 2010)
Collaborate in cryomodule production?
3 sites in the USA
3 FELs - NIR, MIR, FIR. NIR could operate simultaneously with MIR, but maybe with less power. NIR is upstream of MIR. Swept-frequency operation would be difficult, but there is not much demand, so will just do spot measurements
Coherent Undulator for Terahertz Spectroscopy (CUFT)
Draft design of light source overseen by George Neil.
USD2.5M
1. Design of user facility ('co-location')
2. Research into pulse manipulation using electrostatic accelerator
Parameters:
Injector/dump 10 MeV - thermionic gun
Linac 60 MeV
1m to 1mm wavelengths, plus THz
3 or 4 wigglers - rapid tunability, well-defined polarisation states
Current? 1mA, peak 45A
Bunch repetition rate? Variable bunch trains. 0.5 to 20 ps bunch length, 11.8 MHz repetition rate either pulsed or CW, 0.3% energy spread
1.3 GHZ RF
Emittance 20 mm-mrad
10-20 fs timing jitter - how is it used? (ask George Neil)
NIR lt 60 MeV 1.6 kW
MIR lt 30 MeV 700 W (will actually be 60 MeV because FELs using same electron bunches simultaneously)
FIR 7-10 MeV 300W
Interest is in use of FEL light in combination with high magnetic fields. Fields up to 180 Tesla available at LANL!! (pulsed)
LANL - 65/90 T pulsed fields available to users.
FSU site - 45 T DC field available to users (wow). 2 more magnets 25-30 T and 36 T (so-called series connected design which makes operation and interlocks simpler).
(need to watch out where you site the accelerator, and use passive shielding to reduce the stray fields from the DC magnets).
Experimental need - 1ps, pump-probe, THz to near-IR.
Timeline (hoped)
2008 funding (NSF only) - about 25-30M (not including staff or building)
2012 completion
Detail design - 2008/2009 (15 staff-years).
Make some of it? (injector for 2010)
Collaborate in cryomodule production?
Tuesday, April 24, 2007
2D-IR Meeting - 24th April 2007
No AP work has been done since the 2D-IR meeting. FEL work has reviewed differing options for the RF module and bunch repetition rate.
The latest agreed configuration (v1.2) is the original CDR configuration (2 FELs not operating together).
George Neil has made comments that JLab is considering some similar solutions (perhaps with Talahassee).
Perhaps this paper: http://www.bessy.de/fel2006/proceedings/PAPERS/TUPPH009.PDF
Having 2 FELs from one electron beam, the action of one FEL disturbs the electron beam for the next FEL. It is an open question whether these two FELs can output at the same wavelength (to be considered by Neil Thompson) - same-wavelength operation would allow 'on the diagonal' measurements to be made.
It could be possible to use only coherent emission from an undulator rather than an FEL - it is not clear whether an FEL would offer any pulse length advantage (i.e. can it generate shorter pulses than coherent emission alone?), or is this just a limit from the wavelength?
Post-meeting comment - of course, if we have coherent emission at a certain wavelength, then there is no point in having an FEL, as the cavity will not cause any microbunching. Recall that an FEL only works at wavelengths shorter than the bunch length; microbunching of a bunch can't occur at length scales bigger than the bunch (think about it - it doesn't make any sense!).
Christine Ramsdale has considered some of the controls/DAQ aspects.
Mark's notes:
-----------------------------
The full suite of FELs to provide complete coverage of the wavelength region requested by David Klug would not be available on day 1 but a phased introduction of facilities is envisaged.
Neil Thompson agreed to look at feasibility of Dual undulator / 2 FELs in one cavity before 25 May. Then to investigate if coherent undulator radiation could also be used, but significant longer pulse lengths expected to be a problem due to slippage. FMQ noted that George Neil may already have proposed a solution for 2 FEL outputs with one injector system- HO will speak to him.
UV-vis detection pulse would be provided by down converting the UV-FEL radiation. This has the advantage of maintaining high rep rate compared to table top laser system.
MB confirms that can transport FEL light with good efficiency and to provide spot size required.
It was agreed that this experiment would be an ideal system to develop data acquisition for. GRM agreed to initiate a flow diagram for this.
The latest agreed configuration (v1.2) is the original CDR configuration (2 FELs not operating together).
George Neil has made comments that JLab is considering some similar solutions (perhaps with Talahassee).
Perhaps this paper: http://www.bessy.de/fel2006/proceedings/PAPERS/TUPPH009.PDF
Having 2 FELs from one electron beam, the action of one FEL disturbs the electron beam for the next FEL. It is an open question whether these two FELs can output at the same wavelength (to be considered by Neil Thompson) - same-wavelength operation would allow 'on the diagonal' measurements to be made.
It could be possible to use only coherent emission from an undulator rather than an FEL - it is not clear whether an FEL would offer any pulse length advantage (i.e. can it generate shorter pulses than coherent emission alone?), or is this just a limit from the wavelength?
Post-meeting comment - of course, if we have coherent emission at a certain wavelength, then there is no point in having an FEL, as the cavity will not cause any microbunching. Recall that an FEL only works at wavelengths shorter than the bunch length; microbunching of a bunch can't occur at length scales bigger than the bunch (think about it - it doesn't make any sense!).
Christine Ramsdale has considered some of the controls/DAQ aspects.
Mark's notes:
-----------------------------
The full suite of FELs to provide complete coverage of the wavelength region requested by David Klug would not be available on day 1 but a phased introduction of facilities is envisaged.
Neil Thompson agreed to look at feasibility of Dual undulator / 2 FELs in one cavity before 25 May. Then to investigate if coherent undulator radiation could also be used, but significant longer pulse lengths expected to be a problem due to slippage. FMQ noted that George Neil may already have proposed a solution for 2 FEL outputs with one injector system- HO will speak to him.
UV-vis detection pulse would be provided by down converting the UV-FEL radiation. This has the advantage of maintaining high rep rate compared to table top laser system.
MB confirms that can transport FEL light with good efficiency and to provide spot size required.
It was agreed that this experiment would be an ideal system to develop data acquisition for. GRM agreed to initiate a flow diagram for this.
Wednesday, April 18, 2007
Seminar - A.Terekhov, 18th April 2007
4GLS photoinjector problems:
10ps response decreases QE
Low (30 meV) energy spread decreases QE
100 mA on cathode needs 50 W laser, needs cooling
100 mA gives short lifetime due to ion back-bombardment
Solve the first 3 using new cathode heterostructure design - the response time depends on the number of random walks through the thickness of the cathode. A cathode with a thin active later is therefore better. But QE drops because of incomplete light absorption, and mean transverse energy can increase.
In reflection mode (RM), can use Distributed Bragg Reflector
In transmission mode (TM), can use Graded Band Gap Layer - can increase QE by maybe 10x.
Band bending near surface can increase transverse energy spread via momentum scattering (and 'acceleration'), up to value of negative electron affinity. This is not the longitudinal energy spread, however, the longitudinal and transverse energy spreads are similar (difference between conduction band minimum and vacuum energy level, around 150 meV at 300 K and 250 meV at 100 K.
If active layer thickness is smaller than the characteristic thermalisation length (of the order of 100 nm) then you get bigger energy spread.
10ps response decreases QE
Low (30 meV) energy spread decreases QE
100 mA on cathode needs 50 W laser, needs cooling
100 mA gives short lifetime due to ion back-bombardment
Solve the first 3 using new cathode heterostructure design - the response time depends on the number of random walks through the thickness of the cathode. A cathode with a thin active later is therefore better. But QE drops because of incomplete light absorption, and mean transverse energy can increase.
In reflection mode (RM), can use Distributed Bragg Reflector
In transmission mode (TM), can use Graded Band Gap Layer - can increase QE by maybe 10x.
Band bending near surface can increase transverse energy spread via momentum scattering (and 'acceleration'), up to value of negative electron affinity. This is not the longitudinal energy spread, however, the longitudinal and transverse energy spreads are similar (difference between conduction band minimum and vacuum energy level, around 150 meV at 300 K and 250 meV at 100 K.
If active layer thickness is smaller than the characteristic thermalisation length (of the order of 100 nm) then you get bigger energy spread.
Wednesday, April 11, 2007
Notes from 4GLS Physics Meeting 11th April 2007
Forthcoming milestones:
Wakes
Diagnostics
Main linac quads position fixed
Magnet spreader specification fixed - apertures
Magnet spreader design
BC1 optimisation - report due
BC2 optimisation - Sara
Collimators in HACL arcs - Hugh
Beam loss brainstorming - David 27th April
Longitudinal cavity wakefields of 7-cell cavity design and HOM dampers - Emma/Carl? late June
Wakes
Diagnostics
Main linac quads position fixed
Magnet spreader specification fixed - apertures
Magnet spreader design
BC1 optimisation - report due
BC2 optimisation - Sara
Collimators in HACL arcs - Hugh
Beam loss brainstorming - David 27th April
Longitudinal cavity wakefields of 7-cell cavity design and HOM dampers - Emma/Carl? late June
Thursday, April 05, 2007
Notes from ERLP Planning Meeting 5th April 2007
Late Saturday Shift 2/3 go to 350 kV. If there is something wrong,
Heat cleaning on Monday.
Activation on Tuesday.
No problems at 250 kV
Halo - overheating of the cathode? Diffusion of arsenic to the surface of the cathode causing scattering of the incoming laser light rather than reflection through the anode.
Tasks:
Highest Q available
Emittance measurement? No sensible results possible with the halo. For example, a pepperpot measurement revealed a lot of strange images.
Heat cleaning on Monday.
Activation on Tuesday.
No problems at 250 kV
Halo - overheating of the cathode? Diffusion of arsenic to the surface of the cathode causing scattering of the incoming laser light rather than reflection through the anode.
Tasks:
Highest Q available
Emittance measurement? No sensible results possible with the halo. For example, a pepperpot measurement revealed a lot of strange images.
Wednesday, April 04, 2007
Notes from ERLP Planning Meeting 4th April 2007
The halo is around 50% of the beam. This number is not confirmed, so we should try to repeat the measurement using a scanning slit.
Make sure that no cryo equipment is left on the floor at the end of cryo commissioning.
Yuri/Philippe on Shift 1
Make sure that no cryo equipment is left on the floor at the end of cryo commissioning.
Yuri/Philippe on Shift 1
Tuesday, April 03, 2007
Notes from ERLP Planning Meeting 3rd April 2007
Next 2 shifts should look at fringing field in the first correct after SOL-01 (HCOR/VCOR-06). There appears to be a lot of (cruciform) distortion at large apertures (i.e. large corrector angles).
The present halo could be because of laser scattering inside the gun chamber (has the foil been removed? yes it has). The halo is more-or-less round (as seen on screen A) - it could be an image of the whole cathode (with the laser spot in the middle). The edge of the halo is the edge of the wafer?
Anode has a 20mm radius. Since the laser beam comes in at ~6 deg, the image at the cathode should be a clipped 'ellipse' shape. Maybe about half the charge is in the halo? Needs to be measured (by Steve Jamison).
Shield wall has not been replaced since removal for installation of another transfer line girder module.
Any time we get a good average current (e.g. 20 pC), then call Martin Holbourn to do some radiation measurements.
2 options - work at 250 kV to look at source of halo. Or go to 350 kV hoping that the halo will diminish, but could kill cathode. For the next 2 shifts we will therefore work at 250 kV.
The present halo could be because of laser scattering inside the gun chamber (has the foil been removed? yes it has). The halo is more-or-less round (as seen on screen A) - it could be an image of the whole cathode (with the laser spot in the middle). The edge of the halo is the edge of the wafer?
Anode has a 20mm radius. Since the laser beam comes in at ~6 deg, the image at the cathode should be a clipped 'ellipse' shape. Maybe about half the charge is in the halo? Needs to be measured (by Steve Jamison).
Shield wall has not been replaced since removal for installation of another transfer line girder module.
Any time we get a good average current (e.g. 20 pC), then call Martin Holbourn to do some radiation measurements.
2 options - work at 250 kV to look at source of halo. Or go to 350 kV hoping that the halo will diminish, but could kill cathode. For the next 2 shifts we will therefore work at 250 kV.
Monday, March 05, 2007
Discussion of min/max 4GLS energies 5th March 2007
Magnet designs going 550->600 MeV would be different
RF 550->600 MeV is increased gradient rather than power (check with Peter?)
Cryogenic load would be increased going 500->600 MeV
Collimation depth 550->600 would be increased
Water cooling 550->600 would be increased
CSR emitted power in HACL 550->600 MeV would increase.
Could consider and increase of energy with a decrease of current, to allow greater exploration of undulator output wavelength.
Twin-line variability:
We can straightforwardly change the HACL energy by turning off the XUVFEL.
In the present spreader design the energy ratio is fixed. So
550->600 MeV means 750 MeV->818 MeV on XUVFEL (for same energy ratio), so therefore XUVFEL injector goes 210->228 MV (assume same phases in everything) - the phase might be possible to change (but is complicated!)
The change 540->590 is 9%
The change 210->228 is 8%, so this can be done
So output energy of XUVFEL would now be 818 MeV.
Lower limit is around HACL 450 MeV - no real lower limit identified yet, except perhaps wakes (cavity/resistive and CSR) inducing larger energy spread on the bunch. The VUVFEL may stop working.
Upper limit on cavities is 20 MV/m, which is about 650 MeV. It is agreed to cost items (magnets, collimators, PSUs etc.) at 650 MeV (HACL). Need to work out what this is in XUVFEL line.
It was agreed that no inter-line energy variability is assumed - if operating together, the energy ratio is fixed at 550/750.
RF 550->600 MeV is increased gradient rather than power (check with Peter?)
Cryogenic load would be increased going 500->600 MeV
Collimation depth 550->600 would be increased
Water cooling 550->600 would be increased
CSR emitted power in HACL 550->600 MeV would increase.
Could consider and increase of energy with a decrease of current, to allow greater exploration of undulator output wavelength.
Twin-line variability:
We can straightforwardly change the HACL energy by turning off the XUVFEL.
In the present spreader design the energy ratio is fixed. So
550->600 MeV means 750 MeV->818 MeV on XUVFEL (for same energy ratio), so therefore XUVFEL injector goes 210->228 MV (assume same phases in everything) - the phase might be possible to change (but is complicated!)
The change 540->590 is 9%
The change 210->228 is 8%, so this can be done
So output energy of XUVFEL would now be 818 MeV.
Lower limit is around HACL 450 MeV - no real lower limit identified yet, except perhaps wakes (cavity/resistive and CSR) inducing larger energy spread on the bunch. The VUVFEL may stop working.
Upper limit on cavities is 20 MV/m, which is about 650 MeV. It is agreed to cost items (magnets, collimators, PSUs etc.) at 650 MeV (HACL). Need to work out what this is in XUVFEL line.
It was agreed that no inter-line energy variability is assumed - if operating together, the energy ratio is fixed at 550/750.
Tuesday, February 27, 2007
EMMA Design Review 27th February 2007
Day 2
RF Requirements - Scott Berg
RF Aperture 34.751 mm (diameter), assumes 0.439 mm offset
Flanges can be different sizes, maybe can help put up the shunt impedance
Also add 3mm for phase-space-painted energy spread/dispersion in ring
BPMs can resolve 16 pC vertically and 25 pC horizontally.
50 um resolution is what is required.
RF Requirements - Scott Berg
RF Aperture 34.751 mm (diameter), assumes 0.439 mm offset
Flanges can be different sizes, maybe can help put up the shunt impedance
Also add 3mm for phase-space-painted energy spread/dispersion in ring
BPMs can resolve 16 pC vertically and 25 pC horizontally.
50 um resolution is what is required.
Monday, February 26, 2007
EMMA Design Review 26th February 2007
Neil Bliss - Specification Update
Can there be a window between ERLP and EMMA? Check this action - we know that the emittance is increased, but what about the energy spread and bunch length.
Run ERLP at lower gradient? Need to run some S2E simulations with lower gradient. Check after Bruno's presentation.
People have been talking about 19 cavities rather than 21.
Geometry of magnets has been changed to make F and D parallel in each cell now.
F magnet translation has reduced substantially to only a few mm.
RF cavity length has been increased 105 to 110 mm to increase the shunt impedance.
Field clamp plates have been added to the engineering drawing.
Injection by Carol may be on inside of the ring. This raises the possibility of having the ring anticlockwise rather than clockwise.
Single girder option is being considered - arc sections would be machined and then linked together.
When the quadrupoles move, their fields will push on each other and therefore move the magnets slightly on their slides. This effect needs to be examined.
Scott Berg - Lattice Update
The lattice elements in one cell are now all co-parallel; a very small increase in apertures
Frequency range in cavities has to be increased to allow scanning over energy range.
The end field in the magnets causes a horizontal position shift at large apertures, which affects the required aperture (it jumps at the end of the magnets, when plotted longitudinally).
Energy spread/length in input bunch may affect the energy spread, and therefore dispersion, and therefore aperture, in the ring. Need to check the longitudinal emittance and give to Scott.
The FODO option is basically discounted.
The RF cavities are offset from the cell centre-line, at least in the model, by about 0.5mm.
Modelling requirements;
Stefan Tzenov will look at modelling ERLP injector at 10 MeV, and estimate the injection parameters. Injection phase may be random (no sync lock between RF systems) and then measured, or instead synchronisation can be attempted.
Ideal emittance is about 12 mm-mrad. See if 10 mm-mrad is possible from the injector.
Check slice energy spread, projected energy spread, bunch length, peak current and longitudinal emittance from ERLP at this energy.
Can there be a window between ERLP and EMMA? Check this action - we know that the emittance is increased, but what about the energy spread and bunch length.
Run ERLP at lower gradient? Need to run some S2E simulations with lower gradient. Check after Bruno's presentation.
People have been talking about 19 cavities rather than 21.
Geometry of magnets has been changed to make F and D parallel in each cell now.
F magnet translation has reduced substantially to only a few mm.
RF cavity length has been increased 105 to 110 mm to increase the shunt impedance.
Field clamp plates have been added to the engineering drawing.
Injection by Carol may be on inside of the ring. This raises the possibility of having the ring anticlockwise rather than clockwise.
Single girder option is being considered - arc sections would be machined and then linked together.
When the quadrupoles move, their fields will push on each other and therefore move the magnets slightly on their slides. This effect needs to be examined.
Scott Berg - Lattice Update
The lattice elements in one cell are now all co-parallel; a very small increase in apertures
Frequency range in cavities has to be increased to allow scanning over energy range.
The end field in the magnets causes a horizontal position shift at large apertures, which affects the required aperture (it jumps at the end of the magnets, when plotted longitudinally).
Energy spread/length in input bunch may affect the energy spread, and therefore dispersion, and therefore aperture, in the ring. Need to check the longitudinal emittance and give to Scott.
The FODO option is basically discounted.
The RF cavities are offset from the cell centre-line, at least in the model, by about 0.5mm.
Modelling requirements;
Stefan Tzenov will look at modelling ERLP injector at 10 MeV, and estimate the injection parameters. Injection phase may be random (no sync lock between RF systems) and then measured, or instead synchronisation can be attempted.
Ideal emittance is about 12 mm-mrad. See if 10 mm-mrad is possible from the injector.
Check slice energy spread, projected energy spread, bunch length, peak current and longitudinal emittance from ERLP at this energy.
Friday, February 23, 2007
4GLS Planning Meeting, 23rd February 2007
Review of configuration v1.2
Things to check:
HACL Injector Energy Spread (uncorrelated)
XUV Injector outline parameters
Review of quadrupole strengths and lengths
Boris to check the geometry and layout of the HACL injector and associated equipment with the engineers
Check that 4m is available at end of XUVFEL Linac 3 for possible laser heater
Borehole investigation is about to start, on Monday 26th February
Artesian groundwater cooling to be investigated
Photon energy ranges required from IR-FEL are still unclear. For the purposes of the next year of design
VUV-FEL 3-10eV
XUV-FEL 8-100 eV
IR-FEL 2.5-25 um, 20 to 200um in two branches - separate operation only! A conceptual overview of alternatives (e.g. the simultaneous Klug scheme) is also to be included.
Things to check:
HACL Injector Energy Spread (uncorrelated)
XUV Injector outline parameters
Review of quadrupole strengths and lengths
Boris to check the geometry and layout of the HACL injector and associated equipment with the engineers
Check that 4m is available at end of XUVFEL Linac 3 for possible laser heater
Borehole investigation is about to start, on Monday 26th February
Artesian groundwater cooling to be investigated
Photon energy ranges required from IR-FEL are still unclear. For the purposes of the next year of design
VUV-FEL 3-10eV
XUV-FEL 8-100 eV
IR-FEL 2.5-25 um, 20 to 200um in two branches - separate operation only! A conceptual overview of alternatives (e.g. the simultaneous Klug scheme) is also to be included.
Thursday, February 22, 2007
Chat with John Dainton
Just had a chat with John, and showed him all the great things you can do with Blogger.
AP Group Meeting 22nd Feb 2007
ASTeC Risk Register - to be reviewed.
EuroFEL booking and projections to be reviewed.
ASTAB Meeting - presentations went well.
4GLS funding - core project unlikely to be funded before 2010.
Group objectives - 4GLS and EuroFEL, HLO to do.
Bids for next FY - consider AP work.
EuroFEL booking and projections to be reviewed.
ASTAB Meeting - presentations went well.
4GLS funding - core project unlikely to be funded before 2010.
Group objectives - 4GLS and EuroFEL, HLO to do.
Bids for next FY - consider AP work.
Thursday, February 15, 2007
CI Symposium - 15th February 2007
Mike Poole - ASTeC and the history of Daresbury Laboratory
1957 - Wilkinson proposes HE e synchrotron
1960 - Cockcroft + Cassels propose 4 GeV version
1961 - Cockcroft proposes Cheshire site
1962 - NINA approved
Proposed sites: Macclesfield, Crewe, Winsford, Risley, Skelmersdale
1963 - Daresbury selected
Mike Poole has some great photos of the history of the lab.
1957 - Wilkinson proposes HE e synchrotron
1960 - Cockcroft + Cassels propose 4 GeV version
1961 - Cockcroft proposes Cheshire site
1962 - NINA approved
Proposed sites: Macclesfield, Crewe, Winsford, Risley, Skelmersdale
1963 - Daresbury selected
Mike Poole has some great photos of the history of the lab.
Monday, February 12, 2007
CICT/CI/ASTeC Support Meeting, 12th Feb 2007
Notes and actions:
I.Bailey - to do website updates on new CI web server during interim period.
J.Dainton - to discuss with M.Poole who will be website manager and to arrange that person to take over management of the website.
G.McBain - to look at option of filtering all CI outgoing mail at mailserver to appear to come from @cockcroft.ac.uk.
H.Owen/J.Smith - to circulate how to change 'Reply-to' addresses in Exchange/Outlook
H.Owen - to check with FBU IT whether all functionality is possible in Sharepoint web access using Firefox.
Decision - Arrange with B.Runcie and S.Eyres to do design and update of CI website.
J.Dainton - to provide budget code for website work.
C.Dean/J.Smith/H.Owen - to put printer Linux PPD files onto CI website.
G.McBain - to check IMAP/POP3 instructions for offsite email access for all types of users.
H.Owen - to email H.Gun-Why about site information for non-staff.
M.Enderby - to propose recommendations for CI data backup, e.g. server-based? on-site/off-site options, best practice instructions? strategy?
I.Bailey - to do website updates on new CI web server during interim period.
J.Dainton - to discuss with M.Poole who will be website manager and to arrange that person to take over management of the website.
G.McBain - to look at option of filtering all CI outgoing mail at mailserver to appear to come from @cockcroft.ac.uk.
H.Owen/J.Smith - to circulate how to change 'Reply-to' addresses in Exchange/Outlook
H.Owen - to check with FBU IT whether all functionality is possible in Sharepoint web access using Firefox.
Decision - Arrange with B.Runcie and S.Eyres to do design and update of CI website.
J.Dainton - to provide budget code for website work.
C.Dean/J.Smith/H.Owen - to put printer Linux PPD files onto CI website.
G.McBain - to check IMAP/POP3 instructions for offsite email access for all types of users.
H.Owen - to email H.Gun-Why about site information for non-staff.
M.Enderby - to propose recommendations for CI data backup, e.g. server-based? on-site/off-site options, best practice instructions? strategy?
Thursday, February 08, 2007
4GLS AP Meeting 8th Feb 2007
Martin's seminar on radiation protection - no change in our collimation/machine protection philosophy at the moment.
David Holder will book a meeting to brainstorm ideas about beam loss philosophy.
Spreader design - need to review once energy choice is made.
David Holder will book a meeting to brainstorm ideas about beam loss philosophy.
Spreader design - need to review once energy choice is made.
Wednesday, February 07, 2007
4GLS Layout Meeting 7th Feb 2007
Actions:
Boris Militsyn to provide draft HACL injector layout to engineers, including indications of power supply heights.
Simon Appleton to provide detailed layouts of v1.2 including internal cavity dimensions
Julian McKenzie to check that he has the correct x-section of HACL injector model.
Neil Thompson to check he has provided XUV-FEL ID layout information (quads); also minimum height for ID modules.
Boris Militsyn to provide draft HACL injector layout to engineers, including indications of power supply heights.
Simon Appleton to provide detailed layouts of v1.2 including internal cavity dimensions
Julian McKenzie to check that he has the correct x-section of HACL injector model.
Neil Thompson to check he has provided XUV-FEL ID layout information (quads); also minimum height for ID modules.
Tuesday, January 30, 2007
Notes from 2D-IR Meeting, 30th Jan 2007
Requirements:
High sensitivity
High throughput
High information content
DOVE 2D-IR: Doubly Vibrationally Enhanced - Four Wave Mixing
Mix at sample of interest: two tuneable pulse IR fields of omega-1 and omega-2
Make sure field intensities are high enough, 10^10 W cm^-2
Observe an output nonlinear field
Model compound: Benzene
2ps delay between pulses - perhaps up to 5ps
2000 wavenumber scan size
Resolution required for Fermi resonance separation
Ideal spec (200) 500-800 nm , and 2um to 200um.
2ps is a typical required pulse length - i.e. 1ps FWHM.
Time delay variable 0-20ps
Jitter specification - something like <1ps FWHM. But interesting is the noise spectra and how that relates to the integration time in the experiment.
FEL harmonics are either useful or can be filtered out.
High sensitivity
High throughput
High information content
DOVE 2D-IR: Doubly Vibrationally Enhanced - Four Wave Mixing
Mix at sample of interest: two tuneable pulse IR fields of omega-1 and omega-2
Make sure field intensities are high enough, 10^10 W cm^-2
Observe an output nonlinear field
Model compound: Benzene
2ps delay between pulses - perhaps up to 5ps
2000 wavenumber scan size
Resolution required for Fermi resonance separation
Ideal spec (200) 500-800 nm , and 2um to 200um.
2ps is a typical required pulse length - i.e. 1ps FWHM.
Time delay variable 0-20ps
Jitter specification - something like <1ps FWHM. But interesting is the noise spectra and how that relates to the integration time in the experiment.
FEL harmonics are either useful or can be filtered out.
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