PEPPo Readiness Review Presenters:Joe Grames, JLAB (PI) Eric Voutier, LPSC (PI) Reviewers:Hari Areti...

PEPPo Readiness Review Presenters:Joe Grames, JLAB (PI) Eric Voutier, LPSC (PI) Reviewers:Hari Areti Mike Bevins Doug Higinbotham Kelly Mahoney Keith Welch February 3, 2012

Outline PEPPo - Joe Experiment in a nutshell Role of CEBAF injector Experiment Apparatus - Joe Beam line description (includes readiness status and machine protection issues element by element) Beamline Commissioning Experiment Detectors - Eric Modeling The Detector Systems (w/ status and commissioning plan for each) Annihilation Detector Fiber Array Detector Compton transmission polarimeter Data Acquisition and Analysis Data Taking Plan Our punchlist !

PEPPo is proposing to measure the polarization transfer from a polarized electron beam to positrons in the 2-8 MeV/c momentum range. In the production target T 1 : Longitudinal e - (P e- ) produce elliptical whose circular (P ) component is proportional to P e-. P transfers to e + into longitudinal (P e+ ) and transverse (P t ) polarization components. On average P t =0. PEPPo I e = 1 A T 1 = 1 mm Solenoid + aperture defines transverse acceptance DD and adjustable slit define momentum acceptance T1T1 T2T2 S1S1 S2S2 D D PtPt P e- Calorimeter e+e+ e-e- e + annihilates in T 2 Yields polarized photons Compton Polarimeter measures photon polarization to infer positron polarization Anticipated Result Start with a beam of polarized electrons from the CEBAF injector

Context of the SLAC E-166 Experiment 10 MeV Circularly Polarized Photons

PEPPo is proposed to run at the injector, taking advantage of the existing experimental capabilities that uniquely define with precision the CEBAF polarized electron beam at creation. Electron Polarization Controls (Px, Py, Pz) Variable Electron Energy (2-8 MeV) Electron Energy Measurement (1%) PEPPo Laser Electron Intensity Controls (100 pA up to 4 uA) Electron Polarization Measurement (1%)

Spectrometer Mott Electron Polarimeter Faraday Cup (Beam Stop) BCM PEPPo

Vacuum System Valve isolates PEPPo vacuum space Interlocked with upstream/downstream ion pumps Valve will trip if beam line vacuum >1E-7 Torr Distributed ion pumps Pressure

High Current Power Supplies 300A EMI 125A Sorenson Polarity Relays 240V Power Generic Magnet Controls PC104 based DAC/ADC LCW/Thermal Interlocks Relays EPICS interfaced All hardware in place + powered Testing on loads completed, ready for magnet hookup 2011 due date competed w/ 6MSD => now mid-Feb

Class 1 Magnet Lead Enclosures MPC5D02 300A MPD5D03 300A (bipolar switch) MPA5D05 60A (bipolar switch) Covers = 3/8 lexan Signs to be posted Final approval by DSO

Beam Position & Profile Monitoring Fiber Array Detector - X/Y distribution Beam position monitors - X/Y position - Electrons only Viewers - Video profile of position, size, aspect - Electrons upstream of T1 - Electrons/Positrons downstream of T1

Beam Current Monitoring Reconversion Target (T2) - Electrically isolated - Measured by picoammeter Faraday Cup - Electrically isolated - Measured by picoammeter Collimators - tungsten - Electrically isolated - Measured by I to V BCM - Power Meter - Fast receiver => FSD

Production Target (T1) Out (retracted) Viewer (chromox) #1 (0.1 mm, W) #2 (0.5 mm, W) #3 (1.0 mm, W)

Dump and Collimators L shaped dump is 2.5 steel backed by 8 lead (air) Left/Right collimators are 1 tungsten on harp assembly Copper rod 0.5 OD to air cooled baffles + thermocouples Independently electrically isolated for current monitor

PEPPo Faraday Cup Copy of 1kW water cooled injector Faraday Cup LCW interlocked to FSD

Reconversion Target (T2) Reconversion target is 2mm tungsten composite (Densimet D17K) with nominal composition 90.5%W, 7% Ni, 2.5% Cu, mounted in a thin-walled aluminum holder Electrically isolated for current monitoring, with overvoltage protection circuit Illuminated by Al Ladder: T= 96C(Melt = 933C) => W target: T = Ladder + 10C (Melt = 3400C) Engineering Division Performed initial thermal calculations for thin vacuum window Will request additional calculations to more carefully understand envelope

Constraining Beam Current BCM Cavity Faraday Cup #2 Gigatronix (EPICS = slow) Old receiver (1 channel hi or lo, resolution poor, no FSD or EPICS) New receiver (2 channel hi & lo, nA resolution, w/ FSD + EPICS) Calibration against FC2 EPIC recording V2F for DAQ 250nA noise floor Threshold for fast FSD 1 2 3

Constraining Beam Energy J. Dumas, J. Grames, E. Voutier, Upper limit of the electron beam energy at the CEBAF 2D injector spectrometer and its functionality, JLAB TN-08-086 Constrained by limit 2 SRF cavities operate without generating a beam line or wave guide vacuum fault (outgassing and field emission). 8.4 MV/m 6.1 MV/m Warm Region Gain

EPICS slow controls using EDM Prototype screen for commissioning ready => will evolve

Study transport of electron beam over 2-8 MeV energy range Study deposition of electron beam power into elements Study collection and diagnostic of degraded electron beam Study collection and diagnostic of positrons Commissioning Philosophy in 7 easy steps. (closer to ~70 in Commissioning Plan)

1. Transport electron beam and terminate in final vacuum cross ELECTRONS X-RAYS POSITRONS Condition ModeElectron (spec=beam) Electron Energy 6.3 MeV Electron Current

PEPPo Readiness Review Presenters:Joe Grames, JLAB (PI) Eric Voutier, LPSC (PI) Reviewers:Hari Areti...

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