POLARIZED SOURCE LASER OPTICS STUDIES AT UVA

Transcription

1 Progress Report POLARIZED SOURCE LASER OPTICS STUDIES AT UVA Caryn Palatchi, Paschke Lab 1

2 Motivation We are considering changing the Pockels Cell RTP Pockels cell scheme Directly relevant to MOLLER Relevance to PREX indirectly in that: If RTP Pockels cell scheme is completed by the time PREX runs, We can use the RTP Pockels cell during PREX Currently, we are refining our alignment techniques with the RTP cell 2

3 pd Pockels Cell KD*P - Deadtime transition + ringing ~ 100μs PC pol At 2kHz helicity switching, 100μs deadtime is 20% loss of data 3

4 Swapped KD*P for RTP Cell KD*P Cell RTP Cell Attempting to drive cell harder results in greater ringing, 4% amplitude Min 35μs transition + ringing Observe Virtually no ringing (<0.2%) Faster transition 17μs 4

5 Pockels Cell RTP - Deadtime transition ~ 12μs when drive harder At 2kHz helicity switching, 12μs transition Deadtime reduced by 10x 5

6 Anatomy of Cell: KD*P & RTP KD*P Cell RTP Cell 40mm 10mm 60mm 6mm Longitudinal Cell Larger aperture - 10mm Quarter wave voltage ~2400V Two crystals, transverse field Smaller aperture - 6mm Quarter wave voltage ~800V No piezoelectric ringing between DC and 100kHz 6

7 Pockels Cell Setup Polarizer (horizontal) laser 7

8 IHWP RHWP Pockels Cell Setup Polarizer (horizontal) Pockels Cell (Quarter Wave Retardance) laser +/- HV P.C. 8

9 IHWP RHWP Pockels Cell Setup Polarizer (horizontal) Pockels Cell (Quarter Wave Retardance) Analyzer (vertical/45 ) Quad Photodiode Detector laser +/- HV Asymmetry along vertical S1 P.C. Asymmetry along 45 S2 9

10 Pockels Cell Setup Polarizer (horizontal) Pockels Cell (Quarter Wave Retardance) Analyzer (vertical/45 ) Quad Photodiode Detector laser +/- HV Minimize Asymmetry along vertical S1 P.C. Minimize Asymmetry along 45 S2 10

11 IHWP RHWP Pockels Cell Setup Quad Photodiode Detector Pockels Cell Analyzer Polarizer (horizontal) 11

12 HCBA across cell face: S1 KD*P Cell RTP Cell Aq has saddle point in S1 RTP qualitatively similar behavior over shorter length scale 12

13 HCBA Spatial Variation, S1 ~160,000ppm ~22,000ppm ~18,000ppm ~200,000ppm KD*P Cell RTP Cell ~2mmx2mm ~2mmx2mm ~2mmx2mm ~2mmx2mm ~10x larger gradients 13

14 Dx Dx Dy Dy Position Differences, S1 KD*P Cell RTP Cell -7.5 um/mm -40 um/mm X X 7.5 um/mm 45 um/mm Y 6x position difference sensitivity in S1 Y 14

15 HCBA angle dependence,s1 KD*P Cell RTP Cell Saddle point in pitch/yaw 30,000ppm, 4mradx4mrad 50,000ppm, 4mradx4mrad Comparable (OOM) angle dependence in S1 15

16 HCBA angle dependence, S2 KD*P Cell RTP Cell Saddle along pitch/yaw axes Saddle rotated 45deg along pitch+yaw/pitch-yaw axes 16

17 HCBA angle dependence, S2 KD*P Cell RTP Cell ~1000ppm/mrad^2 ~100ppm/mrad^2, 4-40x less variation Aq offset in S2, not correctable with PC. angle 17

18 HCBA correction, S1, S2 KD*P Cell Asymmetry in S1 corrected with voltage, angle Asymmetry in S2 corrected with angle Correct with voltage, angle RTP Cell Asymmetry in S1, correctable with voltage, angle Asymmetry in S2, has very little dependence on angle Correct with voltage, angle S1 S1? Correct with angle Correct with angle S2 S2? 18

19 HCBA angle dependence, S2 KD*P Cell RTP Cell Can t correct residual asymmetry in S2 with angle Even when PC angle is correct (from S1), there remains and asymmetry offset in S2 Correct with voltage, angle Correct with voltage,angle S1 S1 Correct with angle Correct with angle S2 S2 19

20 HCBA angle dependence, S2 KD*P Cell Correct with voltage, angle RTP Cell Asymmetry may be due to intrinsic residual cell birefringence Could correct Asymmetry with compensator Correct with voltage, angle S1 S1 Correct with angle S2 S2 Correct with compensator 20

21 Pockels Cell Setup Polarizer (horizontal) Pockels Cell (Quarter Wave Retardence) Analyzer (vertical/45 ) Quad Photodiode Detector laser +/- HV Asymmetry along vertical S1 P.C. Asymmetry along 45 S2 21

22 Pockels Cell Setup Polarizer (horizontal) Pockels Cell (Quarter Wave Retardence) Compensator Analyzer (vertical/45 ) Quad Photodiode Detector laser +/- HV Minimize Asymmetry along vertical S1 P.C. + compensator Minimize Asymmetry along 45 S2 22

23 Summary, Pros & Cons RTP transition is 12us, 10x less deadtime PRO Qualitatively, behavior of RTP similar to KD*P Asymmetry gradients in S1 are ~10x larger for RTP CON In S1, Asymmetry dependence on angle is comparable In S2, Asymmetry dependence on angle is 4-40x smaller PRO In S2, RTP residual asymmetry offset CON Next steps: Use compensator to correct HCBA offset in S2 Verify can align RTP to same extent as KD*P despite larger gradients, check 4θ minimization with qpd. Then do linear array studies. 23

24 RTP POCKELS CELL STUDIES TO BE CONTINUED Progress Report POLARIZED SOURCE LASER OPTICS STUDIES AT UVA Caryn Palatchi, Paschke Lab 24