PEPPo Readiness Review

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 !

In the production target T1:
Eric Voutier PEPPo is proposing to measure the polarization transfer from a polarized electron beam to positrons in the 2-8 MeV/c momentum range. Start with a beam of polarized electrons from the CEBAF injector Solenoid + aperture defines transverse acceptance T1 T2 S1 S2 D Pt Pe- Calorimeter e+ e- DD and adjustable slit define momentum acceptance e+ annihilates in T2 Yields polarized photons In the production target T1: Longitudinal e- (Pe-) produce elliptical g whose circular (Pg) component is proportional to Pe-. Pg transfers to e+ into longitudinal (Pe+) and transverse (Pt) polarization components. On average Pt=0. Anticipated Result PEPPo Ie = 1 µA T1 = 1 mm Compton Polarimeter measures photon polarization to infer positron polarization XXVth International Workshop on Nuclear Theory

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

Electron Polarization Controls Electron Intensity Controls
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) Measurement (1%) PEPPo Laser Electron Intensity Controls (100 pA up to 4 uA) Electron Polarization Measurement (1%)

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

Vacuum System Valve isolates PEPPo vacuum space
Interlocked with upstream/downstream ion pumps Valve will trip if beam line vacuum >1E-7 Torr Vacuum windows (aluminum 0.010”) Distributed ion pumps Pressure <1E-8 Torr

Thin Vacuum Windows DT < 3° C/uA (Note: Ie- < 1 uA) Al window
(0.010”) 4.5” Copper Gasket 4.5” Copper Gasket Engineering Division Analysis SPECIFICATION No. ACC S-1001 K. Wilson (Stress Analysis) J. Feingold (Thermal) D. Machie (Approval) K. Wiseman (Approval) Burst Test Analysis (Target Group) 0.005” Al failed edge gasket 65psi 0.010” Al failed edge gasket 165 psi Power Deposition (GEANT4) DT < 3° C/uA (Note: Ie- < 1 uA)

Magnets System Quadrupole Control dispersion, size, aspect
Settings for T1 or T2 Solenoids Electron transport Positron collection Dipole Steering Coils Horizontal/Vertical Position/Angle at T1 Spectrometer (D,D-bar) Define central momentum Steering Coils Horizontal/Vertical Position/Angle at T2

Regions 0-1 (Electron Beam)
MBV (red dipole) – Measured MBH (correctors) – Vendor MQD (quadrupoles) – Measured Region 0 Region 1

Region 2 (Collection Magnets)
MPC (capture solenoid) – Measured MPD (spectrometer) – Measured Region 2

Region 2 (Collection Chamber)
Beam Dump (SS) Collimators (left/right) Mask (SS) Viewer

Regions 3-4 (Diagnostic/Polarimter)
MCS (correctors) – Calculated MPT (solenoid) – Measured MPA (analyzer) – Measured Region 4 Region 3

Regions 3 (Transport Solenoid)
Conservative C Un-cooled OK for commissioning, but will replace w/ LCW cooled for experiment 10 MeV 1 MeV

Magnet Power Supplies All power supplies are managed in service building 12 magnets powered by 1A or 10A trims from common bi-polar bulk PS controls (EPICS) 3 magnets powered by 300A (EMI) or 125A (Sorenson) w/ generic DAC/ADC controls (EPICS) Polarity reversal for spectrometer and analyzing magnet achiever w/ high current relay Magnet Name PS Type Current Bipol Rack & Num. Hard Limit Soft LCW/ Klixon Hyst FMAP MBH5D00H Trim 1 A Y IN04B10 – 28 No N / N N BH MBH5D00V IN04B10 – 29 MQD5D00 10 A IN04B10 – 01 Y / N QD MBH5D00AH IN04B10 – 30 MBH5D00AV IN04B10 – 31 MQD5D01 IN04B10 – 02 MPC5D02 EMI 300 A IN02B22 – 01 295 Y / Y TBD MPD5D03 Relay IN02B22 – 02 MPD5D03A NL01B04 – 21 2 A =Cur MCS5D03H IN04B10 – 23 3 A MCS5D03V IN04B10 – 24 MPT5D04 NL01B04 – 20 5 A MCS5D04H IN04B10 – 25 MCS5D04V IN04B10 – 26 MPA5D05 Sorenson 125 A IN02B22 – 03 60 Note: Class 1 magnets (high current, low voltage) are shown in red.

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

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

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

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

Production Target (T1) Out (retracted) Viewer (chromox) #1 (0.1 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 <100 nA, but tested to max beam current <1uA

Analyzing Magnet Iron Core
Analyzing magnet is 7.5cm iron core Meant to attenuate x-rays If target removed exposed to <1uA

Beam Power Deposition Incoming electron kinetic energy [MeV] 2 5 10 Element Name Material Thickness [mm] Power norm to 1uA Production Target = 0.1mm Tungsten 0.1 0.312 0.181 0.158 Production Target = 0.5mm 0.5 1.007 1.676 1.185 Production Target = 1mm 1 1.013 2.554 3.093 Production Target = 2mm 1.022 2.650 4.920 Beam Dump (Spectrometer) 304 Steel 63.5 1.375 3.541 7.022 Collimator 25.3 1.045 2.889 6.107 Vacuum Exit Window Al 0.254 0.078 0.076 Reconversion Target Densimet 1.065 2.747 4.855 Analyzer Magnet Iron 75 1.354 3.505 7.060 Target + Ladder Calculation from R. Michaels (1uA on 1mm W ~ 2.5 Watts) => Al Ladder: DT= 96C (Melt = 933C) => W target: DT = 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
Faraday Cup #2 BCM Cavity Calibration against FC2 EPIC recording V2F for DAQ 250nA noise floor Threshold for fast FSD 1 3 Gigatronix (EPICS = slow) Old receiver (1 channel hi or lo, resolution poor, no FSD or EPICS) 2 New receiver (2 channel hi & lo, nA resolution, w/ FSD + EPICS)

Constraining Beam Energy
Constrained by limit 2 SRF cavities operate without generating a beam line or wave guide vacuum fault (outgassing and field emission). Warm Region Gain <0.6 MeV SRF Region Gain < 7.4 Total Energy < 8.5 MeV 8.4 MV/m 6.1 MV/m Leff = 0.5m J. Dumas, J. Grames, E. Voutier, “Upper limit of the electron beam energy at the CEBAF 2D injector spectrometer and its functionality”, JLAB TN

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

Commissioning Philosophy…
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 …in 7 easy steps.  (closer to ~70 in Commissioning Plan)

ELECTRONS X-RAYS POSITRONS
1. Transport electron beam and terminate in final vacuum cross ELECTRONS X-RAYS POSITRONS Condition Mode Electron (spec=beam) Electron Energy 6.3 MeV Current <100 nA Pulsed Stop Viewers Faraday Cup

2. Transport electron beam thru window to polarimeter for first time. ELECTRONS X-RAYS POSITRONS Condition Mode Electron (spec=beam) Electron Energy 6.3 MeV Current <100nA Pulsed Stop Reconversion Target T2

3. Transport electron beam over energy range 2-8 MeV ELECTRONS X-RAYS POSITRONS Condition Mode Electron (spec=beam) Electron Energy 2-8 MeV Current <100 nA pulsed Stop Reconversion Target T2

4. Transport <1 uA CW to T2 for first time (insert all elements) ELECTRONS X-RAYS POSITRONS Condition Mode Electron (spec=beam) Electron Energy 6.3 MeV (initially) 2-8 MeV Current <1 uA CW Stop Reconversion Target T2

5. Use T1 to study collection with “degraded” electrons ELECTRONS X-RAYS POSITRONS Condition Mode Electron (spec < beam) Electron Energy 6.3 MeV (initially) 2-8 MeV Current <1 uA CW Stop T1 (incident electrons) T2 (degraded electrons)

6. Transport <5 uA CW for first time (test dump with/without T1) ELECTRONS X-RAYS POSITRONS Condition Mode Positron (spec = off) Electron Energy 6.3 MeV (initially) 2-8 MeV Current <5 uA CW Stop Dump w/o T1 in Dump w/ T1 in

ELECTRONS X-RAYS POSITRONS 7. Use T1 to study collection of positrons
Condition Mode Positron (spec =< beam) Electron Energy 6.3 MeV (initially) 2-8 MeV Current <5 uA CW Stop T1 (incident electrons) T2 (degraded positrons)

Polarized Electrons for Polarized Positrons
Eric Voutier PEPPo from the Detector Side Polarized Electrons for Polarized Positrons Fiber array detector Compton transmission polarimeter Annihilation detector XXVth International Workshop on Nuclear Theory

The Experiment Detectors
Eric Voutier The Experiment Detectors (as viewed from downstream of the Compton Polarimeter) XXVth International Workshop on Nuclear Theory

PEPPo Models Simulation Softwares ELEGANT G4Beamline G4PEPPo
Eric Voutier Simulation Softwares PEPPo Models ELEGANT is the PEPPo platform for studies and optimizations of the beam optics along the beam line from several meters up-stream of the 5 MeV dipole down to the reconversion target T2. G4Beamline allows to investigate further the beam optics and the possible beam interactions with the PEPPo beam line components. G4PEPPo is the PEPPo physics platform to study the sensitivity and the performances of the different detectors, and develop the analysis software. ELEGANT G4Beamline G4PEPPo 5 MeV Dipole Newport News, January 27, 2012 XXVth International Workshop on Nuclear Theory

Readiness Simulation Softwares
Eric Voutier Simulation Softwares Readiness Parameter Task Status ELEGANT Verify configuration for element geometry Verify magnetic description for elements Verify method to update model with beam based measurements Verify method to save/restore optics and generate “snap” files Verify method to generate optics for production T1 or reconversion T2 80% 75% 20% - G4Beamline Complete collection simulation for positrons G4PEPPo Completed analyzing power simulation for electrons and positrons 25% Sum Simulation Software Acceptance NO The essential goal of ELEGANT and G4Beamline is to acquire an accurate knowledge of the beam optics that can be confronted to experimental data obtained from the different beam diagnostics along the PEPPo line. The most important objective of G4PEPPo is to predict the analyzing power of the Compton transmission polarimeter to be confronted to experimental data with a known polarized electron beam. Newport News, January 27, 2012 XXVth International Workshop on Nuclear Theory

Operational Status Annihilation Detector Co60 Na22
Eric Voutier Annihilation Detector Operational Status Purpose: the annihilation detector is a diagnostic device intending to sign the presence of e+ by measuring the two 511 keV g’s from e+ annihilation in an insertable target at the exit of the 2 dipoles spectrometer. Nature: 2 NaI(Tl) scintillators 5.1x5.1 cm2 + PMT read-out. Signal integral Co60 Signal integral Na22 Newport News, January 27, 2012 XXVth International Workshop on Nuclear Theory

Commissioning Plan Annihilation Detector Prior Beam Operation
Eric Voutier Annihilation Detector Commissioning Plan Prior Beam Operation 22Na radioactive source measurements in the tunnel enclosure Beam-off background measurements During Beam Operation Opportunistic measurements of the signal-to-background ratio Dedicated Beam Operation Measurement of electron-induced e+ annihilation (electron mode) Measurement of Møller scattering of incident electron beam (electron mode) Measurement of direct e+ annihilation (positron mode) Newport News, January 27, 2012 XXVth International Workshop on Nuclear Theory

Fiber Array Detector Operational Status
Eric Voutier Fiber Array Detector Operational Status Purpose: the fiber detector array is the last beam diagnostic of the PEPPo line intending to measure the e- and e+ beam profiles at the entrance of the Compton transmission polarimeter for characterization of the optics models of the line. Nature: 2 perpendicular layers of 16 scintillating fibers 1x1 mm2 + multi-anode PMT read-out. The counting rate per fiber and above an adjustable threshold is recorded via the EPICS system for further analysis. Newport News, January 27, 2012 XXVth International Workshop on Nuclear Theory

Fiber Array Detector Commissioning Plan Prior Beam Operation
Eric Voutier Fiber Array Detector Commissioning Plan Prior Beam Operation Radioactive source measurements in the tunnel enclosure Beam-off background measurements Dedicated Beam Operation Electron beam scan (electron mode) Measurement of e- beam profile (electron mode) Measurement of e+ beam profile (positron mode) Newport News, January 27, 2012 XXVth International Workshop on Nuclear Theory

Compton Transmission Polarimeter
Eric Voutier Compton Transmission Polarimeter Operational Status Purpose: the Compton transmission polarimeter determines the polarization of the e- and e+ beam by measuring the asymmetry of polarized photon absorption in a longitudinally polarized target, with respect to the beam helicity or the target polarization orientation. Nature: a 2 mm (W) reconversion target (T2) + analyzing magnet (2.3 T) polarizing an iron core (~7%) + 9 CsI(Tl) scintillating crystals 6x6x28 cm3 + PMT read-out. 22Na Data Comparaison of 22Na experimental data with simulations showing the detection of the correlated 511 keV and 1274 keV significant of uncollimated source measurements. 22Na Simulations Newport News, January 27, 2012 XXVth International Workshop on Nuclear Theory

Analyzing Magnet Compton Transmission Polarimeter
Eric Voutier Compton Transmission Polarimeter Analyzing Magnet The measurement of the magnetic flux generated in the pick-up coils upon variation of the analyzing magnet current, together with an accurate knowledge of the magnetic field allow to determine the absorption target polarization (7.5 cm Fe). Flux measurement with a Precision Digital Integrator (PDI). Model of the magnetic flux (OPERA-2D) to reproduce field maps measured at JLab. Newport News, January 27, 2012 XXVth International Workshop on Nuclear Theory

Commissioning Plan Compton Transmission Polarimeter
Eric Voutier Compton Transmission Polarimeter Commissioning Plan Prior Beam Operation 22Na, 137Cs, 60Co radioactive source measurements Beam-off background measurements During Beam Operation Opportunistic measurements of the signal-to-background ratio Dedicated Beam Operation Measurement of Compton transmission asymmetry for a known e- beam (electron mode) Measurement of false asymmetries (electron mode) Measurement of direct helicity correlated position differences (electron mode) XXVth International Workshop on Nuclear Theory

Data Taking Modes Data Acquisition System
Eric Voutier Data Acquisition System Data Taking Modes The PEPPo DAQ is built around the FADC250, developed by the JLab electronics group, which samples the ADC signal at a frequency of 250 MHz and allows for 3 data taking modes: Sample mode ( samples of 4 ns duration per event); Semi-integrated mode (1 sample integral per event, 1 histogram per helicity gate); Integrated mode (1 integral per helicity gate event). The PEPPo DAQ allows for different read-out trigger configurations depending on the purpose of the data taking: background or radioactive source or cosmics measurements, LED monitoring data, physics asymmetry measurements, and annihilation detector data. Newport News, January 27, 2012 XXVth International Workshop on Nuclear Theory

Readiness Data Acquisition System
Eric Voutier Data Acquisition System Readiness Parameter Task Status Hardware Verify module and spare (VME Controler, FADC, TDC, VTOF, Scalers, Discriminator, Gate generator) + cabling Multi-trigger set-up 90% 75% Firmware Development of the FADC250 firmware for integrated mode Verify CODA read-out Verify sample mode operation Verify semi-integrated mode operation Verify integrated mode operation Mass storage - 80% 100% 50% Analysis Measure helicity correlated charge asymmetry Measure helicity correlated position differences Measure Mott asymmetry with PEPPo DAQ Measure Compton transmission asymmetry with electron Sum DAQ Acceptance NO The good operation of the PEPPo DAQ will be validated by measuring the Mott asymmetry to be identical to the one measured with the current Mott DAQ, and ultimately by measuring the Compton transmission asymmetry for a known electron beam. Newport News, January 27, 2012 XXVth International Workshop on Nuclear Theory

Data Analysis Readiness 134Cs? Eric Voutier ~620 keV ~840 keV
Parameter Task Status Decoder Verify data decoding for the 10- and 12-bit FADC250 Verify data decoding of the VME/TDC Verify n-tuple maker for each DAQ configuration 50% 75% Analyzer Verify sample data analysis Verify semi-integrated data analysis Verify integrated data analysis Implement/verify on-line asymmetry measurement 90% - 60% Sum Data Analysis Acceptance NO In-time signals ~620 keV ~840 keV 134Cs? Software sample integral Out-of-time signals Newport News, January 27, 2012 XXVth International Workshop on Nuclear Theory

PEPPo Experimental Program
Eric Voutier PEPPo Experimental Program Data Taking Plan p(e-) (MeV/c) I(e-) P(e-) (%) Time (h) Commissioning 2 – 6 1 nA – 1 µA ≥ 85 105 Mott Measurements 6 1 – 5 µA 10 e- Calibration 30 pA – 1 nA 85 Detector Measurements 6.8 1 – 4 µA 36 e+ Measurements 100 Total 336 Detector commissioning accounts for ~35 h of the PAC38 approved beam time. Newport News, January 27, 2012 XXVth International Workshop on Nuclear Theory

Our Punchlist # Issue Resolution 1 High current PS’s overdue
DC power group raised priority, aiming Feb. 15th 2 300A EMI PS control range small Test regulation, alternatively need replacement supply 3 BCM FSD not ready EES working on FSD output now; deploy next ~weeks 4 Limiting resistors on 6 magnets 2 hour access to complete job 5 Class 1 enclosures not ready 2 hour access to complete job and get DSO approval 6 Two magnets mis-wired 2 hour access to repair wiring 7 Complete magnet B vs. I tables < week to complete analysis, generate tables 8 Model of analyzer magnetization Preliminary model OK; Opera model due in April 9 Analyzer pick-up not instrumented Implement the PDI , and with PS current readback 10 Thermal analysis only preliminary Engineering analysis for more accurate envelope I>1 uA 11 Polarimeter CsI sensitive to x-ray dose 9 crystals => Must=1, Should=5, Like=9 12 Transport solenoid current limit Fabricate high current MPT (+8 wk) + install (+1 wk) 13 Integrated mode of FADC250 Need firmware upgrade from Fast Electronics Group 14 Detector HVPS read back unstable Request to ENG to repair sampling on ADC board 15 Modeling based on preliminary design Repeat simulations on final configuration 16 Beam/detector analysis tools not matured Analysis tools nominally functional by April 1st

Summary The PEPPo Apparatus has been designed to carry out the approved measurements efficiently Careful attention has been paid to protecting the integrity of the CEBAF injector for a variety of accident scenarios Pre-Commissioning of the various elements and protection systems is in good shape The plan for commissioning the apparatus with beam and then carrying out the measurements is well thought out The “Punch list” of remaining items is sensible (and modest in length)

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