1. Compton electron detector R&D

2. Compton polarimetry Compton electron Compton photon

3. Best Compton polarization SLAC SLD Compton polarimeter 0.5 % with electron detection – 41.6 GeV – Large dispersion – 11 Hz EIC – High repetition rate : 10MHz to 750 MHz – Lower energy – Smaller dispersion, more space constraints

4. MEIC Storage ring – Ring ring 748.5 MHz = 1.33 ns bunch structure 3 A at 3 GeV and 180 mA at 11 GeV 2 macrobunch with one polarization 2.3 us Every electron bunch crosses every ion bunch Measure polarization average of the two macrobunch Warm large booster (up to 25 GeV/c) Warm 3-12 GeV electron collider ring Medium-energy IPs with horizontal beam crossing Injector 12 GeV CEBAF Pre-booster SRF linac Ion source Cold 25-100 GeV/c proton collider ring Three Figure-8 rings stacked vertically Electron cooling 6/27/20144 A. Camsonne EIC Users meeting

5. MEIC beam parameters F. Lin--- Beam energyGev3567911 Beam current A 332.01.10.40.18 Total SR power MW 0.493.825.285.385.355.37 Linear SR power density kW/m 1.027.8710.8811.0811.0111.06 Energy loss per turn MeV 0.171.272.644.8913.3729.84 Energy spread 10 -3 0.340.560.680.791.011.24 Longitudinal damping time ms 83.618.110.46.63.11.7

6. MEIC Bunch Structure In Collider Ring 6 … … … … Empty buckets 1.33ns 748.5MHz Polarization (Up) Polarization (Down) bunch train & polarization pattern in the collider ring Empty buckets 2.3μs, ~1700 bunches

7. MEIC Bunch Pattern for Continuous Injection 7 duty factor 6.9e-4 …… 100 ms (~4 damping time) 1s,, I ave =6μA Macro bunch train Detector duty factor 0.98 duty factor 4.3e-4 …… 1.33 ns, 748.5 MHz 173.5 pC 2.3μs, ~1700 bunches 173.5 pC 1.33 ns, 748.5 MHz 2.3μs, ~1700 bunches …… duty factor 0.0167 …… 60s I ave =100 nA 1 second At 100nA average injected current, P equ /P 0 > 96% for the whole energy range

8. Time structure Bunch to bunch : 1.33 ns Polarization state : 2.3 us Top off : 1 min Measure asymmetry for one laser state and polarization Can generate more macro bunches for systematics check, time max for measurement is 2.3 us + 3.7 us - 3.7 us

9. ERHIC 5 GeV to 21.2 GeV 9.4 MHz Repetition rate 50 mA with “Gatling gun” design up to 24 sources Need to measure each sources polarization 80 % min polarization Similar recirculation to CEBAF 6/27/20149 A. Camsonne EIC Users meeting

10. eRHIC beam parameters 50 mA with up to 24 sources 10.8 MHz repetition rate ERL LINAC allows helicity structure with helicity flip from the source Need individual measurement of each source – 100 ns max for each measurement – Logic signal to flag which source is recorded Rates sufficient to measure all sources in a few minutes

11. Compton rates Green laser, 1.3 degrees crossing angle beam 350 um EnergyRate ( kHz/W/A) Max current (A) Rate kHz/W eRHIC current (A) Rate (kHZ/W) 331639480.05 15.8 529838940.05 14.9 629025800.05 14.5 72831.1311.30.05 14.1 92690.4107.60.05 13.4 112580.1846.440.05 12.9 laser of a few watts : 10 KHz to 1 MHz - sufficent statistics in a few seconds 1000 W cavity : rates from tens of KHz to MHz level ( if background high )

12. Simulation background Bremstrahlung Halo 1 kW green laser Halo ( electrons around beam envelope) contribution modeled on Babar PEP II at SLAC Background significant in photon detector Compton signal rate at MHz level : 1% statistical error in s Photon detector signal Electron detector signal 6/27/201412 A. Camsonne EIC Users meeting (Dave Gaskell)

13. Simulation background Bremstrahlung Halo Photon detector signal Electron detector signal 6/27/201413 A. Camsonne EIC Users meeting Bremstrahlung Halo 2 cm cavity aperture1 cm cavity aperture signal to noise ratio improves at high energy for electron detector Background is worse for photon detector Need to pay attention to apertures which can generate background from halo Laser choice depends on background contribution : need more simulation

14. Compton asymmetry e +  e’ +  ’ (( ) (( ) 6/27/201414 A. Camsonne EIC Users meeting

15. Exploring Compton polarimeter in low-Q 2 chicane Same polarization as at the IP due to zero net bend Non-invasive continuous polarization monitoring Polarization measurement accuracy of ~1% expected No interference with quasi real photon tagging detectors c Laser + Fabry Perot cavity e - beam Quasi-real high-energy photon tagger Quasi-real low-energy photon tagger Electron tracking detector Photon calorimeter Possible implementation in low Q 2 for MEIC 6/27/201415 A. Camsonne EIC Users meeting

16. 6/27/201416 e p Polarimeter Laser laser polarization needs to be monitored eRHIC lepton polarimeter: Location? Compton photon detector A. Camsonne EIC Users meeting Option to measure at IP with empty hadron bunch Measure after dipole in machine ? Dedicated chicane ? Constraint on detector technology for the Gatling gun design : detectors signal less than 100 ns ( E. Aschenauer )

17. Requirements for an EIC Compton electron detector Spatial resolution for energy calibration High rate capability High radiation hardness

18. Silicon strip detector

19. Current Hall A setup Vertical motion

20. Issues with Hall A detector Sensitive to background ( low energy photons ? ) Need large amount of shielding Dark current increase rapidly Signal to noise ratio small because of cable length and electronics bus

21. Diamond detector Hall C used Diamond detector Signal smaller but faster and better radiation hardness than silicon detector Still need to determine the rate capabillities and radiation hardness

22. Hall C Compton Electron Detector Diamond microstrips used to detect scattered electrons  Radiation hard: exposed to 10 Mrad without significant signal degradation  Four 21mm x 21mm planes each with 96 horizontal 200 μm wide micro-strips.  Rough-tracking based/coincidence trigger suppresses backgrounds (D. Dutta Missipi State University)

23. Hall C Compton Electron Detector Gain : 200 mV (10x10 3 ) x (1.6x10 -19 ) = 120 mV / fC Diamond detector read out using Custom amplifier-discriminator (QWAD) Output pulse relatively long after amplification – time scales of order 1 μs  Counting at high rates challenging – operate in integration mode Need figure showing this: Dipangkar?

24. Budget diamond detector Itemprice 2 Diamond strip planes 25K$ Feedthrough 9 K$ Vacuum chamber 10 K$ Detector holder 2 K$ Motion system 8 K$ Total 58 K$ Overhead 32 K$ Total over 2 years90 K$

25. Quartz detector PREX experiment First integrated measurement with dE/dx detector Quartz Pure Cerenkov Integrated method – No deadtime correction – Can handle very high rates – Radiation hard of the order of 1 MRad

26. PREX detector principle Thin quartz to reduce shower Light collection through internal reflection PMT readout in integrated mode PMT Quartz electrons Cerenkov photons

27. Tracking-Integrating Hybrid System Quartz detector lacks segmentation, so no “built-in” knowledge of the analyzing power from fitting spectrum  Will investigate using microstrip detector in tandem with chunk of quartz  Periodic measurements at lower luminosity will allow use of strip detector to constrain analyzing power

28. Budget Quartz Itemprice Semiconductor photosensor for vacuum 10K$ Dedicated quartz pieces 10 K$ Detector holder 2 K$ Total 22 K$ Overhead 13 K$ Total over 2 years35 K$

29. Proposal Hybrid detector diamond strip and quart detector Diamond strip in front to determine the asymmetry and response function at low and high rate Quartz

30. Micromegas detector R&D for small edge MM detector as alternative to silicon Readout similar to silicon detector Bulk process to laminate J10 Frame in front of readout Gas tightness using mylar or kapton PCB Mesh lamination Glue J10 frame Glue kapton Foil on frame Bulk Micromegas

31. Micromegas detector Micro horizontal drift chamber HVMicromegas Side readout Drift electrons are detected on the side by a Micromegas Detector designed to be easily replaceable

32. Budget Micromegas Itemprice PCB gerber design 7 K$ PCB board 3 K$ Mesh 1 K$ Supplies 2 K$ Connectors 0.5 K$ Gas box 0.5 K$ Total 13 K$ Overhead 7 K$ Total over 2 years20 K$

33. Roman pot