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.
Tuesday, May 22, 2007
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.
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