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
1. The injector group got their first experience with the new strained layer superlattice GaAs crystals during a real experiment (Happex He and a little bit of hydrogen).
2. To check whether or not helicity-correlated properties will be significantly different at 800 MeV, we plan to submit a test plan to run at 1 pass beam energy.
3. HAPPEx managed to get pretty good position differences with no position feedback.
4. Results on microwave cavity monitor electronics were obtained in Hall A; the electronics still needs more work; continued work on this is planned in Hall A during the fall.

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 
Equations come from section of Edwards and Syphers (eqs and
3.118)
The figure comes from Chao's talk chao_adiabatic_damping.doc.
The expected adiabatic damping now is correct (uses momentum at
100 keV kinetic energy).

4. G0 results on "adiabatic damping" from PZT scans
100 keV
5 MeV
3 GeV
The data in this plot comes from the table in adiabatic_damping_table_26nov.ps
Expected damping factors are:
100 keV -> 5 MeV : 3.9
5 MeV -> 60 MeV: 3.5
60 MeV -> 3 GeV: 7.0
total = 95
Missing damping seems to be in the 100 keV -> 5 MeV region.
Strictly speaking, the position modulations are proportional to the damping factor x sqrt(beta). We have not removed
beta from these figures (since we don't know it), so the damping figures are "modulo beta variations".
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, GeV
(x damping ~ 21, y damping ~ 49)
2. Jan. 2005, all done with "superlattice" GaAs
3 pass, GeV (complicated by large induced charge asymmetry)
1 pass, GeV (dedicated test)
2 pass, GeV (dedicated test)

6. Results from Superlattice Crystal
Strained superlattice GaAs has been in use throughout January 2005
Ordinary strained GaAs strained superlattice
QE % as high as 1%
Polarization % %
Analyzing power % % (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) ppm/V ppm/V
superlattice (before spot move) 3620 ppm/V ppm/V
superlattice (after spot move) ppm/V 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.
Ask if anybody has input or sees anything missing in this plan. Tell them that we intend to submit it next week.
Other facts: We can do this at our expected beam current of 80 microamps since that is the beam current that Hall C will be using. The laser will be the same (a 499 MHz Ti:Saph) that we expect to use during G0 backangle running.

7. Results of Adiabatic Damping
1-pass
R_PZTx (um/V) R_PZTy (um/V) 1I 1I
0I02A 0L 0L 0L 0R
C20A H
H00A
H00B
BPM 1I ppm/V ppm/V
2-pass
R_PZTx (um/V) R_PZTy (um/V) 1I 1I
0I02A 0L 0L 0L 0R
C20A H
H00A
H00B
BPM 1I ppm/V 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.