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Addenda/Errata to Previous Minutes
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Items of Discussion
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¥ Achieve "nominal" beam parameters for FEL operation - 350 keV - 135 pC - 8 p mm-mrad (norm. rms) - 50-70 degrees - 20-40 keV-degrees ¥ Achieve stable operation at 350 kV ¥ Develop a procedure to reproduce beam conditions using only ¥ diagnostics that will be in the FEL injector
SHOULD
¥ Operation at >350 kV ¥ Perform parameter studies to understand gun physics - Rap 0.5, 1.0, and 2.0 mm - Charge/bunch from ~0.1 - 250 pC ¥ Emittance measurements vs solenoid settingsIf done properly, the last item satisfy all other goals except operation at voltages > 350 kV.
Comparison of ITS and FEL Injector Diagnostics
Diagnostic In ITS? In 10 MeV ITS? Laser Spot profile at cathode yes yes Solenoid centering yes yes Beam Current yes ? Light Box Harp ? ? ax, bx, ex at 350 keV yes no DE vs f yes no Bunch length at 350keV yes no ef yea, maybe no Spot before unit no yes 10 MeV diagnostics no yes
¥ Need harp scans at light box during 350 keV runs to develop a reference for later 10 MeV studies. ¥ Does/Will gap monitor work? ¥ Must have sufficient data base of runs at 350 keV to be somewhat confident of 10 MeV ITS beam.
Outline of Experimental Plan I. Calibration/Testing of equipment (1 week) A. Hardware checkout B. Cavity gradient vs kick calibration C. Beam with cavity tests D. Determine setting lens 2 that produces minimum spot size at the slit E. Determine setting lens 2 that produces minimum spot size at straight ahead harp F. Determine minimum DE for low charge bunches II. Beam Experiments at 250 keV - Cavity effects (2-3 days) A. Several preselected points matching previous 250 keV data B. Look for significant discrepancies (making emittance worse) III. Parameter Studies (24 hours per aperture setting) A. Rap = 0.5, 1.0, and 2.0 mm B. Q from 0.3 pC to 400 pC C. Data 1. Size at Light Box 2. Transverse emittance and Energy Spread at slit 3. Bunch Length at Aperture 4. Energy Tilt/Longitudinal Emittance 5. Beam current IV. Lifetime studies A. Average will be high when aperture is in B. The cathode will be in a hostile environment Work Remaining to be Done ¥ Automation of the longitudinal data taking (2 weeks) ¥ Data analysis (2 weeks) ¥ Finalizing parameter sets (1 week) - Beam conditions - Lens settings - Error analysis/noise levels of each set - Poisson comparison of new solenoid ¥ Finish beam line installation ¥ Install cathode stalk (~1st week of January) ¥ Bake/activation ~3 weeks Estimated time for first beam: Feb. 1 Summary of Parameters - PARMELA Ipeak = 0.01 Amps, sr = Rmax st [psec] Rmax[mm] Q [pC] 4sf[deg] 4sE[keV] 4ef[keV-deg] exrmsN[p mm-mrad] 4efslice[keV- deg] 15 0.5 0.38 33 0.35 1.5 0.14 0.3 25 0.5 0.63 54 0.31 2.5 0.15 0.3 15 1.0 0.38 33 0.48 2.5 0.3 0.4 25 1.0 0.63 54 0.46 4.2 0.3 0.4 15 2.0 0.38 33 0.8 4.7 0.6 0.8 25 2.0 0.63 54 0.81 7.9 0.6 0.8 Ipeak = 0.27 Amps, sr = Rmax st[psec] Rmax[mm] Q[pC] 4sf[deg] 4sE[keV] 4ef[keV-deg] exrmsN[p mm-mrad] 4efslice[keV-deg] 15 0.5 10 37.3 3.2 7.0 0.6 0.8 25 0.5 16.7 58 2.7 12 0.7 0.3 15 1.0 10 36 3.33 8.2 0.7 0.3 25 1.0 16.7 57 2.84 13 0.8 0.5 15 2.0 10 35 3.0 8.0 0.9 0.8 25 2.0 16.7 56 2.6 13.4 1.0 0.7 Ipeak = 1.0 Amps, sr = Rmax st[psec] Rmax[mm] Q[pC] 4sf[deg] 4sE[keV] 4ef[keV-deg] exrmsN[p mm-mrad] 4efslice[keV-deg] 15 0.5 38 45 6.3 10.4 1.8 0.5 25 0.5 63 65 6.1 20 2.4 0.5 15 1.0 38 42 7.3 14 1.7 0.5 25 1.0 63 63 6.9 25.5 2.0 0.5 15 2.0 38 40 7.5 16 2.1 0.9 25 2.0 63 61 7.4 30.4 2.4 1.0 Ipeak = 2.7 Amps, sr = Rmax st[psec] Rmax[mm] Q[pC] 4sf[deg] 4sE[keV] 4ef[keV-deg] exrmsN[p mm-mrad] 4efslice[keV-deg] 15 0.5 100 55 9.5 16 11 0.9 25 0.5 167 15 1.0 100 52 11.5 18 4.0 0.5 25 1.0 167 72 12 35 5.4 0.8 15 2.0 100 47 13 23 4.0 1.0 25 2.0 167 69 13.3 45 4.8 1.0 Ipeak = 6.7 Amps, sr = Rmax st[psec] Rmax[mm] Q[pC] 4sf[deg] 4sE[keV] 4ef[keV-deg] exrmsN[p mm-mrad] 4efslice[keV-deg] 15 0.5 250 SCR - - - - 25 0.5 416 SCR - - - - 15 1.0 250 65 17 36 20 1.3 25 1.0 416 72 12 35 5.4 15 2.0 250 60 20 33 8.5 1.3 25 2.0 416 81 21 59 11 1.4 Q = 135 pC, sr = Rmax st[psec] Rmax[mm] Q[pC] 4sf[deg] 4sE[keV] 4ef[keV-deg] exrmsN[p mm-mrad] 4efslice[keV-deg] 15 0.5 135 SCR - - - - 25 0.5 135 71 8.8 26 11 0.5 15 1.0 135 55 13 19 6 0.6 25 1.0 135 69 10 30 4 0.6 15 2.0 135 51 15 26 5 0.7 25 2.0 135 66 11 37 4 1.0 Error Estimates Available power from kicker: 450 W Bunch length: Nominal beam size at straight-ahead harp: 4sx Å 1 mm Bunch lengths to be measured range from 33û to 80û At 200 W, deflection at harp is 5.4û/mm. - For 60û 4s bunch length, 4sx Å 11 mm. (10-to -1) - ~5 degree resolution At 400 W, deflection at harp is 3.8û/mm. - For 33û 4s bunch length, 4sx Å 8.7 mm. (8.8-to-1) - ~4û resolution Longitudinal Emittance Nominal beam size at straight-ahead harp: 4sx Å 0.5 mm At 400 W, deflection at slit is 9û/mm. E-f tilt error Finite beam size at slit causes Å4û of bunch to contribute to energy spread of sampled beamlet. This is a problem when there is significant energy tilt. Nominal 4s energy spreads to measured range from 0.3 keV to 1 keV To make energy error due to tilt small, want energy tilt error <0.1 keV This occurs when when energy tilt slope ts is ts[keV/degree]*4û < 0.1 => ts<0.025 keV/degree Nominal tilts range from 0.1 keV/degree to 0.25 keV/degree Can be deconvoluted Error due to misalignment Å0.05 keV -- assuming 0.3û error in tilts of slit and harp Error due to stray field gradients Å0.05 keV 0 Error due to Energy spread induced by cavity Å0.2 keV -- assuming < 1 mm diameter spot size at cavity Finite Slit Size Error Å0.1 keV _________________________________________________ Additional questions: 1. What is sensitivity to HVPS droop? 2. What is actual laser pulse length? 3. What is sensitivity of longitudinal emittance to solenoid? New Issues ---------- Action Items ------------ Action Priority Items (assigned) ---------------------------------- A-05 2 Injector energy precision Douglas A-06 1 10 MeV dump optics Douglas A-09 1 Dump Instrumentation Legg 6/04/96 A-10 2 Back leg diagnostic placement Douglas A-15 1 Commissioning Procedure Legg, Krafft 5/16/96 A-19 0 Web Documentation Jordan weekly A-20 1 10->42 MeV dump Douglas A-24 1,2 Beam loss Bohn A-29 1 Software Planning for Longer Term Bohn, et al. A-30 1 Burnthrough/Conflat Expansion Denard, Kloppel A-34 2 Consistent Linac phasing plan Yunn A-35 1 simultaneous transverse and longitudinal Kehne/Engwall 8/6/96 A-39 1 report on ARR plan Legg 8/23. A-41 2 Modeling of lower than 10 MeV injector kehne, Liu 10/1/96 A-42 2 2nd gun for long term tests Bohn 10/1/96 A-44 1,2 Start Rui on emittance code Bohn 8/13/96 A-45 1 decide on dump diagnostics Legg/Krafft 9/4 A-46 1 specify the field quality in the dipole shut off to run straight ahead Douglas 9/11 A-47 1 OTR beam interaction number by Denard 9/11 A-54 1 FEL Turn-On Proc S. Benson 11/1/96 A-55 1 Laser Diagnostic Proc Benson 11/1/96 A-56 1 Proposal to vary laser intensity Benson 10/22/96 A-57 1 What is equivalent macropulse to CEBA viewers Legg 10/15/96 Action Items (pending) ------------ P-02 1 Laser phase modulator Jordan P-05 1 Devise fine-tuning procedure for buncher gradient Krafft/Kehne P-08 1,2 How do we change energy? What is the energy range? Benson P-14 1 How is the gun/laser operated? Benson P-15 Discussion on robustness of controls Legg P-18 1,2 Technote by Yunn summarizing machine impedance Yunn P-19 2 Consistent linac/bunching phase sets Yunn P-20 1 Lock plans (who in particular) Johannes? P-21 1 Save/restore plans Benesch P-25 1,2 RF control sensitivities/ Merminga Microphonics Diff for FEL/ Pathlength effect P-28 1,2 Scrapers: Where and How? Bohn, Li P-29 2 FEL/linac interaction Merminga P-30 2 Tracking including realistic wiggler fields Douglas P-35 1 Coordinated ITS beam running/SRF commissioning plan Legg/Bohn/Harwood P-37 1 42 MeV dump design and interlocking Wiseman Agenda for Next Meeting ----------------------- Item Person Responsible Time ---- ------------------ ---- * Review agenda/corrections to minutes Legg 5 min. * 350 keV Shift schedule, the who and how Legg 10 min * ARR update Boyce(?) 20 min * New Issues ALL 10 min * Agenda for next meeting All 5 min.