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Adiabatic Damping and Parity Quality of Low Energy Beam for G0 Backward Angle Running

Adiabatic Damping and Parity Quality of Low Energy Beam for G0 Backward Angle Running R. Suleiman, 8 am Meeting, 01 February 2005. Previous G0 and Happex results: G0 needed position feedback but Happex did not. It appears that Happex got more adiapatic damping.

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Adiabatic Damping and Parity Quality of Low Energy Beam for G0 Backward Angle Running

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  1. Adiabatic Damping and Parity Quality of Low Energy Beam for G0 Backward Angle Running R. Suleiman, 8 am Meeting, 01 February 2005 • Previous G0 and Happex results: G0 needed position feedback but Happex did not. It appears that Happex got more adiapatic damping. • 2. 1 pass beam energy test and experience with "superlattice" crystal in January 2005

  2. Motivation for Helicity-Correlated Beam Properties Test at 1 pass We had some benefit from "adiabatic damping" in the forward angle run (see next slide). What can we expect at the lower beam energies? Will the reduction in adiabatic damping be as expected (about a factor of 0.5 less)? Are there other surprises awaiting us at lower beam energy?  Test plan submitted in September Beam test at 1 pass is completed collected a lot of parasitic data at different passes

  3. Adiabatic Damping of Betatron Oscillations In the case where the particle momentum is a slowly varying function of longitudinal position in accelerator, we have:  Amplitude of betatron oscillation is damped as the beam energy is adiabatically increased From injection energy = 100 keV to typical hall energy ~ 3 GeV, maximum expected adiabatic damping 

  4. G0 results on "adiabatic damping" from PZT scans 100 keV 5 MeV 3 GeV Total observed damping from 100 keV to 3 GeV: x ~ 24, y~ 10 Most of damping comes from 5 MeV  3 GeV region; little damping observed in injector (Chao is needed here)

  5. G0 Beam Tests We take data with all devices (RHWP, IA, PZT, PITA); some dedicated time is available for running with only Hall C beam in machine Data taken: 1. December 2004, strained GaAs, 5 pass, 5.766 GeV (x damping ~ 21, y damping ~ 49) 2. Jan. 2005, all done with "superlattice" GaAs 3 pass, 3.475 GeV (complicated by large induced charge asymmetry) 1 pass, 1.201 GeV (dedicated test) 2 pass, 2.338 GeV (dedicated test)

  6. Results from Superlattice Crystal Strained superlattice GaAs has been in use throughout January 2005 Ordinary strained GaAs strained superlattice QE 0.2 % as high as 1% Polarization 80 % 85 % Analyzing power 5-10% 2% (measured) Large induced charge asymmetries observed for PZT motion: (compare to typical 30 ppm/V observed during G0 forward angle run) x y strained GaAs (Dec. 2004) 388 ppm/V 238 ppm/V superlattice (before spot move) 3620 ppm/V 948 ppm/V superlattice (after spot move) 973 ppm/V 562 ppm/V This could potentially complicate position feedback; we will watch the HAPPEx experience with superlattice this June; we may want to ask for regular strained if the experience is not good.

  7. Results of Adiabatic Damping 1-pass R_PZTx (um/V) R_PZTy (um/V) 1I02 14.01 4.14 1I04 33.45 20.31 0I02A 9.67 15.65 0L03 4.58 1.67 0L04 12.92 6.83 0L06 21.17 12.74 0R05 13.23 7.99 C20A 3.57 0.50 H00 2.97 0.58 H00A 2.97 0.44 H00B 2.85 0.62 BPM 1I02 -564 ppm/V -78 ppm/V 2-pass R_PZTx (um/V) R_PZTy (um/V) 1I02 13.59 3.90 1I04 32.93 19.90 0I02A 10.32 15.86 0L03 4.44 1.65 0L04 14.14 7.44 0L06 24.64 14.11 0R05 14.81 8.44 C20A 1.13 2.85 H00 0.83 1.72 H00A 0.83 1.36 H00B 0.74 1.16 BPM 1I02 -587 ppm/V -144 ppm/V

  8. QE map of superlattice crystal before test The spot was at 620/760. The gradient is clearly bigger in x than y, consistent with our observations.

  9. RHWP Scan

  10. Conclusions and Outlook 1. We got all the data we wanted for now. 2. The pzt induced charge asymmetry is large and will complicate the position feedback (if needed). 3. We see damping at 1-pass and higher passes but position differences are still larger than required.

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