OLYMPUS Collaboration Meeting DESY July 17 18 2008

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

Proposed Experiment • Electrons/positrons (100 m. A) in multi-Ge. V storage ring DORIS at DESY, Hamburg, Germany • Unpolarized internal hydrogen target (buffer system) 3 x 1015 at/cm 2 @ 100 m. A → L = 2 x 1033 / (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

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

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

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

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

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

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 Tech. Etch foils F. Simon et al. , IEEE 2007, ar. Xiv: 0711. 3751

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

GEM foils 70 µm 140 µm Typically 5 mm Cu on 50 mm kapton ~104 holes/cm 2 5 µm 70 µm Chemical etching • R. De Oliveira (CERN-EST) • Tech. Etch (MIT, Bo. Nu. S) • 3 M Corporation Laser drilling • Tamagawa (RIKEN) 55 µm 50 µm``

Multi-GEM Detectors • GEMs can be cascaded for higher gain • Gain of 104 needed for efficient MIP detection Double 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 Triple GEM

Luminosity Monitors (I): Telescopes 2 t. GEM telescopes, 22. 5 msr, 10 o, R=200 cm, d. R=10 cm, 2 tracking planes Forward telescopes 10 o

Luminosity Monitors (I): Telescopes • • • Two symmetric GEM telescopes at 10 o Two-photon effect negligible at high-e / low-Q 2 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 ~1 cm at 10 o Same readout pitch as in MIT prototype (635 mm) Number of electronics channels per telescope: 2 x(300+300)/0. 635 ~= 1900 • •

Luminosity Monitors (I): Telescopes

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

Luminosity Monitors (II): Trackers • Extension of BLAST acceptance at ~5 o-15 o and ± 5 o out of plane • • 30 msr = 28 x 28 cm 2 at 160 cm distance, 40 x 40 at 230, 52 x 52 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 mm) Number of electronics channels per tracker: 2 x(280+400+520)/0. 635 ~= 3800

Luminosity Monitors (II): Trackers

Forward Telescope versus Tracker Telescope Tracker Tracking planes Distance 2 R 1=200 cm R 2=210 cm Gap Solid angle Area/cm 2 d. R=10 cm 22. 5 msr 30 x 30 track segment ~3800 3 R 1=160 cm R 2=230 cm R 3=300 cm d. R=70 cm 30 msr 28 x 28, 40 x 40, 52 x 52 bent tracks ~7500 ~k$ 31. 3 ~k$ 55. 0 total FEE (for two sectors) Total Cost Materials Manpower

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 – C 0 cylindrical and C 1 planar GEM trackers for Time Reversal Experiment with Kaons (TREK) at J-PARC (~2011) – Augment 12 Ge. V 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)