Transcript Document
APS/DNP meeting, Newport Beach, Oct 24-27, 2012 Collimation and tagging instrumentation for the GlueX photon beamline Richard Jones Igor Senderovich, Anne-Marie Carroll University of Connecticut Beamline Overview Radiator Counting House Coherent Bremsstrahlung photon beam Pair Spectrometer Top View Tagging Spectrometer Photon Beam dump 75 m Collimator intensity (/GeV) Electron beam / dump SolenoidBased detector Tagger Area Beam contains both coherent and Collimator Cave Experimental no collimator incoherent components. with collimator Hall D Only the coherent component is polarized. Collimation suppresses incoherent part. APS/DNP meeting, Newport Beach, Oct. 24-27, 2012 Eg (GeV) 2 Tagging spectrometer focal plane hododscope post-bremsstrahlung 12 GeV electrons electrons crystal radiator APS/DNP meeting, Newport Beach, Oct. 24-27, 2012 • 500 scint. fibers • 2mm x 2mm • SiPM readout • 3MHz rate/fiber • st = 200ps 3 Photon collimator photon beam collimator (75m downstream) 12 GeV electrons crystal radiator • 3.4mm aperture • photon “spot” ~5mm RMS • 15% power transmission • shielded alcove APS/DNP meeting, Newport Beach, Oct. 24-27, 2012 4 Collimator requirements dynamic range 0.5 nA – 5mA resolution 200 mm RMS bandwidth > 60 Hz dx < 200 mm robustness • radiation hard • stable gain • reliable APS/DNP meeting, Newport Beach, Oct. 24-27, 2012 5 Collimator design tungsten plates Tungsten pin-cushion design Miller and Walz, NIM 117 (1974) 33-37 measures current due to knockons in EM showers tungsten pins charge asymmetry comes from high-energy delta rays “knock-ons” ee+ incident gamma beam tungsten pin cushion insulating support APS/DNP meeting, Newport Beach, Oct. 24-27, 2012 12 cm 6 Beam test – April 2011 Brendan Pratt prototype detector installed in Hall B photon dump area James McIntyre Igor Senderovich +Alex Somov, Hovanes Egyan APS/DNP meeting, Newport Beach, Oct. 24-27, 2012 7 Run conditions beam energy: 3.36 GeV current: 15 nA, 60 nA precollimator: 2.6 mm radiator: 10-4 radiation lengths, gold stability – very good sampling frequency 333kHz APS/DNP meeting, Newport Beach, Oct. 24-27, 2012 8 Active collimator data sweep collimator horizontally across beam, observe raw currents on wedges APS/DNP meeting, Newport Beach, Oct. 24-27, 2012 9 Active collimator data near the aperture centered at 14.28 cm look at asymmetry Vright– Vleft Vleft + Vright raw offsets not removed gain ~ 15% / mm APS/DNP meeting, Newport Beach, Oct. 24-27, 2012 10 Active collimator data electronic noise is negligible raw asymmetry signal: • moving through beam • out of beam APS/DNP meeting, Newport Beach, Oct. 24-27, 2012 11 Active collimator data results @ 60nA amplifier bandwidth • beam noise floor: 18 mm @ 600Hz • readout noise floor 3 mm @ 600Hz beam noise floor scaling to 0.6nA • readout noise floor digitization noise floor 130 mm @ 120Hz APS/DNP meeting, Newport Beach, Oct. 24-27, 2012 12