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