1. Luminosity Monitor Hampton University, Hampton, VA 23668 Jefferson Laboratory, Newport News, VA 23606 USA OLYMPUS Collaboration Meeting, DESY, July 17-18, 2008 Michael Kohl

2. Proposed Experiment Electrons/positrons (100mA) in multi-GeV storage ring DORIS at DESY, Hamburg, Germany Unpolarized internal hydrogen target (buffer system) 3x10 15 at/cm 2 @ 100 mA → L = 2x10 33 / (cm 2 s) Large acceptance detector for e-p in coincidence BLAST detector from MIT-Bates available Measure ratio of positron-proton to electron-proton unpolarized elastic scattering to 1% stat.+sys. Redundant monitoring of luminosity pressure, temperature, flow, current measurements small-angle elastic scattering at high epsilon / low Q 2

3. Control of Systematics Luminosity monitors OLYMPUS: BLAST @ DORIS 10 o Change BLAST polarity once a day Change between electrons and positrons once a day Left-right symmetry

4. Control of Systematics i = e+ or e- j= pos/neg polarity Geometric proton efficiency: Ratio in single polarity j Geometric lepton efficiency:

5. Control of Systematics Change between electrons and positrons every other day Change BLAST polarity every other day Left-right symmetry Super ratio: Cycle of four states ij Repeat cycle many times

6. Luminosity Monitoring Measure L ij relatively and continuously to ~1%/hour Pressure, temperature, flow, current measurements Moller scattering … Forward-angle (high-epsilon, low-Q) elastic scattering (  e+ =  e- ) At forward angle:

7. Control of Systematics Change between electrons and positrons every other day Change BLAST polarity every other day Left-right symmetry Super ratio: Cycle of four states ij Repeat cycle many times

8. Forward Elastic Luminosity Monitor Forward angle electron/positron telescopes or trackers with good angular and vertex resolution Coincidence with proton in BLAST High rate capability GEM technology? MIT protoype: Telescope of 3 Triple GEM prototypes (10 x 10 cm 2 ) using TechEtch foils F. Simon et al., IEEE2007, arXiv:0711.3751

9. Principle of GEM Detectors Copper layer-sandwiched kapton foil with chemically etched micro-hole pattern gas amplification in the hole GEM = Gas Electron Multiplier introduced by F. Sauli in mid 90’s, F. Sauli et al., NIMA 386 (1997) 531

10. GEM foils 70 µm 140 µm 70 µm 55 µm 5 µm 50 µm`` Typically 5  m Cu on 50  m kapton ~10 4 holes/cm 2 Chemical etching R. De Oliveira (CERN-EST) TechEtch (MIT, BoNuS) 3M Corporation Laser drilling Tamagawa (RIKEN)

11. Multi-GEM Detectors GEMs can be cascaded for higher gain Gain of 10 4 needed for efficient MIP detection Double GEM Triple GEM C. Buettner et al., Nucl. Instr. and Meth. A 409(1998)79 S. Bachmann et al., Nucl. Instr. and Meth. A 443(1999)464

12. Luminosity Monitors (I): Telescopes Forward telescopes 2 tGEM telescopes, 22.5msr, 10 o, R=200cm, dR=10cm, 2 tracking planes 10 o

13. Luminosity Monitors (I): Telescopes Two symmetric GEM telescopes at 10 o Two-photon effect negligible at high-e / low-Q2 Sub-percent luminosity measurement per hour for all energies 22.5 msr = 30 x 30 cm 2 at 200 cm distance Two GEM layers with ~0.1 mm resolution with ~10 cm gap → Vertex resolution (z) of ~1cm at 10 o Same readout pitch as in MIT prototype (635  m) Number of electronics channels per telescope: 2x(300+300)/0.635 ~= 1900

14. Luminosity Monitors (I): Telescopes

15. Luminosity Monitors (II): Trackers Forward trackers 10 o 2 tGEM trackers, 30msr, 10 o, R=160/230/300cm, dR=70cm, 3 tracking planes

16. Luminosity Monitors (II): Trackers Extension of BLAST acceptance at ~5 o -15 o and ± 5 o out of plane 30 msr = 28x28 cm 2 at 160 cm distance, 40x40 at 230, 52x52 at 300 cm Three GEM layers with ~0.1 mm resolution with ~70 cm gap, like WC Same readout pitch as in MIT prototype (635  m) Number of electronics channels per tracker: 2x(280+400+520)/0.635 ~= 3800

17. Luminosity Monitors (II): Trackers

18. Forward Telescope versus Tracker TelescopeTracker Tracking planes 23 DistanceR1=200cmR1=160cm R2=210cmR2=230cm R3=300cm GapdR=10cmdR=70cm Solid angle22.5msr30msr Area/cm 2 30x3028x28,40x40,52x52 track segmentbent tracks total FEE~3800~7500 (for two sectors) Total Cost Materials~k$ 31.3~k$ 55.0 Manpower

19. Providing GEM technology Collaboration HU-MIT Goal: Establish HU/Jlab GEM R&D Center –Howard Fenker / Bonus collaboration –Thia Keppel / Medical physics applications: Hampton University Proton Therapy Institute (HUPTI) under construction –C0 cylindrical and C1 planar GEM trackers for Time Reversal Experiment with Kaons (TREK) at J-PARC (~2011) –Augment 12 GeV program at Jlab (~2013) –Luminosity monitors for OLYMPUS (2010 ???) Funding Request: –IGERT Traineeship / NSF Pre-proposal (April/October 2008) –NSF Nuclear Physics (September 24, 2008) –DOE (October 2008)