1. B. Azmoun BNL RD 51 Collaboration Meeting Stony Brook, NY Oct. 4 2012

2. New Applications for GEM Tracking Detectors at BNL sPHENIX PHENIX → sPHENIX (major upgrade) Augment silicon tracking in central region Large area tracking in forward direction eRHIC Central TPC Planar GEMs in forward direction Need to be low mass for measuring scattered electron Medical Imaging Tracking positrons from PET isotopes → tomography Useful in plant biology → biofuels, environmental science Initial R&D Effort Reconstructing tracks from a beta source Cosmic rays SRS/APV, and first look at the VMM1 chip GEM based PET B. Azmoun, BNL2

3. From PHENIX to Central Detector Forward Spectrometer sPHENIX Smaller, more compact, but with larger acceptance (|  |<1.1,  =2  Central solenoid magnet with high precision silicon tracking with additional GEM tracking Forward spectrometer with large area GEM trackers GEM Tracker s GEM Tracker B. Azmoun, BNL3

4. EIC Detector – Conceptual Design Central Detector Forward/Backward Detectors Large acceptance: -5 <  < 5 Asymmetric Nearly 4  tracking and EMCAL coverage HCAL coverage in central region and hadron direction Good PID Vertex resolution (< 5  m) Electron is scatted over large range of angles (up to 165˚) Low Q 2 → low momentum (few GeV) Requires low mass, high precision tracking GEM TPC Planar GEM Trackers GEM Tracker B. Azmoun, BNL4

5. Mini-Drift GEM Det. + SRS Readout Std. 10x10cm CERN 3-GEM Det. ArCO2 (70/30) Gain ~ 6500 ~17mm Drift Gap Drift Time ~600ns SRS /512 channels APV 25 30 x 25ns Time Samples Martin Purschke’s RCDAQ affords high flexibility COMPASS style Readout: 256 x 256 X-Y Strips ~10cm x 400um pitch Drift Gap Transfer 1 Induction Transfer 2 GEM 1 GEM 2 GEM 3 Mesh X-Y Strips Pitch: 400um 17mm 1.5mm 2mm 1.5mm Preamp/Shaper Primary Charge Fluctuation B. Azmoun, BNL5

6. Data Processing Propagated Errors: Angle: ~+/-18mrad Charge arrival time: ~+/-1.8ns Linear Fit to determine arrival time = x-int. 30 samples x 25ns = 750ns window Raw Data: Waveforms in TimeVector Signature: “Charge square” Vector Recon: X -coord. = middle of pad Y-coord. = drift time * Drift Vel. Fit (x,z) points to line Vector Recon. Z- residual < 0.5mm B. Azmoun, BNL6

7. Some Limitations on Track Recon. For tracks near zero degrees, less pads fire and the track reconstruction gets more ambiguous, leading to larger errors. Here it is better to rely on the centroid for giving the position of the track, where high gas diffusion is preferable. For larger angled tracks, gas diffusion and charge sharing between pads is the major source of error, since the true arrival time of the column of charge above a given pad is distorted. Charge fluctuations on the primary ionization lead to small charge clusters, which can be difficult to measure. This can put a limit on the arrival time calculations at each strip. MC Results on Track Reconstruction ErrorsFluctuations in Primary Ionization T. Cao B. Azmoun, BNL7

8. Measuring Low Energy Collimated Beta Source using External Trigger Plastic Veto Scintillator (5mm) Plastic Trigger Scintillator (0.5mm) ~50mm Sr-90 Brass Source Holder Tungsten Collimator 1.00mm hole Light guide (5mm) External Trigger allows for precise timing of hits, with no dependence on the detector’s ability to measure first pad hit, but… Low momentum electrons suffer greatly from multiple Coulomb scattering by any scintillator used to produce the external trigger Sr90  -decay spectrum Endpoint ~2.2MeV For example, even observe occasional scattering in gas B. Azmoun, BNL8

9. Measuring Betas with Self-Triggered System Several Advantages to having a Self Triggered System: Ease of use, independent readout, and can be used for applications where an external trigger is not readily available GEM trigger doesn’t provide precise timing so rely on ability to measure the first pad fired as a measure of t_ZERO Detector requirements: High Gain Low Noise Wide Drift Gap Low Diffusion Gas (CF4?) Beam cross section @17mm = 2mm Beam Angle = 590 mrad Spread due to beam div./scattering Preamp/Shaper Capacitively couped to bottom GEM electrode ~50mm Sr-90 Brass Source Holder Tungsten Collimator 1.00mm hole GEM TRIGGER 1nF B. Azmoun, BNL9

10. Tracking Cosmics X-AxisY-Axis Top Scintillation Counter Bottom Scintillation Counter Detector Y-Vector Y-Axis (mm) B. Azmoun, BNL10

11. GEM Detector + VMM1 Readout Peak sensing ASIC that provides charge amplitude, and peak-time with minimal time walk Programmable electronic gain, memory depth (we use 1usec) Records only pads with charge above threshold Labview interface allows for Plug n’ Play Despite only spending a day’s worth of time with the chip, we were able to take some reasonable data VMM1  FEC  USB  PCVMM1 Labview Control panel Preliminary Results (64 ch.): Measured Fe55 spectrum Measured Sr90 vectors at ~35 o B. Azmoun, BNL11

12. Medical Imaging: using mini-drift to do PET e-e- e+e+ γ γ e+e+ ~0.2 mm Plant tissue absorbs radioactive tracer  + decay, followed by positron annihilation Traditionally back to back gammas are measured to reconstruct image New Concept: Use mini-drift detector to measure escaping positrons directly Thin plant tissue (eg, Leaf) Positron Escape (50%)Positron Annihilation Fig. C.2.2-5 Escaped positron fraction vs. thickness of [ 18 F]-FDG solution as determined by microPET imaging of our positron escape phantom. B. Azmoun, BNL12 E max (  + )= 640 keV

13. Preliminary Results with FDG (proof of principle) FDG is a radioactive tracer and analog of glucose, commonly used in PET scans Vial of liquid FDG ~1cm mylar window Sigma of Reconstructed position ~5.6mm B. Azmoun, BNL13

14. Summary Used Mini-drift GEM detector to reconstruct vectors from ionization trails using the SRS system with a relatively slow sampling rate ADC(40MHz). Successfully read out a GEM based detector with the VMM1 chip. Successfully measured tracks produced by  + particles and have provided a proof of principle that the mini-drift GEM detector may be applicable for doing PET. Outlook: Will produce high precision, silicon based cosmic ray telescope to study the performance of the detect0r further. Also, we have a beam test at CERN planned later this October for studying the detector under very controlled conditions. B. Azmoun, BNL14