Optical Transition Radiation Monitor for the T2K experiment Mitchell Yu York University 2017/09/18
Overview • The T2K experiment • The Optical Transition Radiation (OTR) monitor • OTR monitor operation history • OTR monitor operation status • Future OTR monitor upgrade plans • OTR foil radiation damage study • Summary 17-09-18 NBI2017 - Mitchell Yu - York University 2
The T2K experiment • The Tokai-to-Kamioka long baseline neutrino oscillation experiment ( T2K ) uses an intense neutrino (antineutrino) beam produced by the collision between J- PARC’s 30GeV proton beam and a graphite target 17-09-18 NBI2017 - Mitchell Yu - York University 3
Optical Transition Radiation (OTR) Monitor proton beam direction • T2K neutrino beam position is reconstructed by using measurements from the ESMs, the SSEMs, and the OTR • The Optical Transition Radiation (OTR) Monitor is the most downstream proton beam monitor located 30cm upstream of the T2K target • The beam profile parameters measured by the OTR are used both for the beam commissioning and for the neutrino flux prediction • 2D beam profile is also reconstructed for the OTR live online monitor (continuous beam position and profile monitoring during physics run) 17-09-18 NBI2017 - Mitchell Yu - York University 4
Optical Transition Radiation (OTR) Monitor • A 50 µm-thick Ti foil is placed between the proton beam target and the collimator • The foil (45 o w.r.t. beam) produces backward optical transition radiation (light produced when charged beam pass through the foil) perpendicular to the beam 17-09-18 NBI2017 - Mitchell Yu - York University 5
Optical Transition Radiation (OTR) Monitor • The OTR optical system consists 4 parabolic mirrors • Transports the light (optical transition radiation) • Harsh environment (5e8 Sv/h) near the target • Camera ( radiation hard CID camera ) placed at a lower radiation area to capture the light 17-09-18 NBI2017 - Mitchell Yu - York University 6
Optical Transition Radiation (OTR) Monitor The remotely rotatable OTR disk has 8 different foils which serve various purposes • No target - no OTR measurement • Ceramic foil – produces fluorescent light with low intensity beam (up to 40kW), used during beam commissioning • Calibration foil – with holes in a grid, used for calibration with external light sources • Titanium foils – Ti1 used during beam operation, Ti2-4 are spares • Cross foil – titanium foil with a cross pattern, used for in beam calibrations “Cross foil” • Currently used in beam 17-09-18 NBI2017 - Mitchell Yu - York University 7
Optical Transition Radiation (OTR) Monitor Calibration foil image • Hole position on the calibration foil in OTR camera surveyed relative to horn axis during installation • Filament or laser light backlights the calibration foil and the images are saved periodically • Hole positions in the calibration foil image and survey results are used for image correction • Absolute position • Distortion correction 17-09-18 NBI2017 - Mitchell Yu - York University 8
Impact of the OTR monitor measurement • Proton beam monitors measurements are extrapolated to calculate the proton beam position and angle at the target • The OTR measurement reduces uncertainties of extrapolation • When OTR data is included: • σ x 0.5 à 0.5 mm • σ y 2.3 à 0.5 mm • σ θ x 0.08 à 0.08 mrad • σ θ y 0.5 à 0.3 mrad • Bigger improvements on Y (off-axis angle) • Vertical (y) bending magnet after SSEM17 • Can only use SSEM18 and SSEM19 (very close together) for extrapolation • OTR measurement provides the 3 rd point for the fit 17-09-18 NBI2017 - Mitchell Yu - York University 9
OTR monitor operation history • OTR1 (slide 11) • Stable operation between 2009 – 2013 OTR2 (slide 12 – 13) • • Assembled, calibrated and tested in 2011 • Operation between 2013 – present • Minor problems appeared from Mar. 2015 • Motor disconnected, OTR disk fixed at cross foil position since Jan. 2016 • OTR3 (slide 14) • Arm, disk, mirror 1-2 tube, mirror 3 tube • Assembled, calibrated and tested in 2014 • Spare system • Exchange rehearsal using the manipulator arm system in the remote maintenance area (RMA) performed in Dec. 2015 • Disk flange replaced • Ti foil modification • OTR4 • Currently being built 17-09-18 NBI2017 - Mitchell Yu - York University 10
OTR1 Operation Status • OTR1 operated stably for 6.6e20 protons on target OTR profile on Ti foil Consistent with beam OTR light linearity 9e13 protons line SSEM monitors with beam intensity 17-09-18 NBI2017 - Mitchell Yu - York University 11
OTR2 Operation Status • Problem with the OTR disk rotation mechanism noticed on Aug. 2015 • Possible disk flange and plunger damage might be the reason • Independent test of the commercial plungers indicate spring failure after large number of compressions • Decided to put the cross foil in beam position and not to rotate the disk to prevent further damage • The OTR monitor has been operating stably with the cross foil since Feb. 2016 • Light yield decreases as exposure increases • Need to change foil before the light yield becomes too low for the analysis • OTR1 Ti2 foil survived 5.0e20 POT • OTR2 Ti1 foil has been exposed to 5.0e20 POT • OTR2 Cross foil has been exposed to 1.1e21 POT • OTR2 still has 3 spare Ti foils to use if needed • No problem for the proposed additional 0.8e21 POT until 2018 Stainless Ti disk steel plunger flange April. 2017 May 2014 Feb. 2016 OTR2 installed Switch to Cross foil 17-09-18 NBI2017 - Mitchell Yu - York University 12
OTR2 Foil Status Future foil radiation damage studies July 2017 inspection August 2015 inspection Ti1 foil: ~5x10 20 POT Ti1 foil: ~5x10 20 POT Cross foil: ~11x10 20 POT Cross foil: ~0x10 20 POT Cross foil Cross foil Ti1 foil Ti1 foil 13 9 August 2017
OTR3 Upgrade Status • Ti disk flange à stainless steel disk flange • Harder surface to prevent damage during disk rotation • Commercial plunger à customized plunger • Customized spring for more robust performance • Machine 4 holes on each Ti foil • For calibration usage • Plan to use Ti-6A-4V (grade 5) foils instead of current Ti-15V-3Cr-3Sn-3Al • Same as in He vessel beam window • Important Ti alloy for post- irradiation studies 17-09-18 NBI2017 - Mitchell Yu - York University 14
OTR1 foil radiation damage studies • OTR1 foils Ti1 foil (Ti-15V-3Cr-3Sn-3Al) are world’s most irradiated Ti specimens • Ti1: 1.6e20 POT • Ti2: 5.0e20 POT • Ti1 foil was transported to PNNL on Jan. 2016 for post- irradiation examination TEM image Elemental mapping • Different grain structure at surface where discoloration is visible • Discolored region at surface made of Si-0/Ti-C layers • Si may come from vessel- evacuating booster-pump oil • Andy Cassela’s talk: PNNL (Graphite/ Ti) in the RaDIATE session Dec 12, 2016 NSERC 2016 Review 15
Future foil radiation damage studies • OTR1 foils (Ti-15V-3Cr-3Sn-3Al) are world’s most irradiated Ti specimens • OTR2 foils (Ti-15V-3Cr-3Sn-3Al) will also be used for future radiation damage studies • Ti1: 5.0e20POT • Cross foil: 1.1e21POT (will be increased) • Potentially 1.9e21POT if OTR operates with the cross foil alone until 2018 • OTR3 will have Ti-6A-4V (grade 5) foils installed • Possible switch to OTR3 in summer 2018 17-09-18 NBI2017 - Mitchell Yu - York University 16
Summary • The Optical Transition Radiation (OTR) monitor measure proton beam profile with Ti foil in the beam using optical transition radiation light • OTR1 operated stably between 2009 - 2013 • OTR2 is current used, it has minor problems but is operating stably • Upgrades are being made on the spare systems OTR3 and OTR4 • OTR1 foils were the world’s most irradiated Ti specimens (5e20 POT) • OTR2 foils will become the world’s most irradiated Ti specimens (1.9e21 POT) • Future OTR will use Ti-6A-4V foils 17-09-18 NBI2017 - Mitchell Yu - York University 17
OTR group • The OTR group built and installed the OTR monitor • Entirely a Canadian responsibility • Led by S. Bhadra (York U.), A. Konaka (TRIUMF) and J. Martin ( U. Toronto ) • Current and former members: • Grad students • Postdocs – Brian Kirby MSc York U. 07 – Alysia Marino U. Toronto (06-09) è UBC PhD è postdoc U. Hawaii è BNL è faculty U. Colorado – Leif Stawnyczy MSc York U. 09 – Mark Hartz U. Toronto /York U.(09-13) – Slavic Galymov PhD York U. 11 è faculty TRIUMF/IPMU è faculty IPNL Leon – Arturo Fiorentini York U. (13- ) – Patrick de Perio PhD U. Toronto 14 • Undergrad students (07-13) è postdoc Columbia U. – Patrick de Perio U. Toronto – Elder Pinzon PhD York U. – Mitchell Yu PhD York U. – Slavic Galymov York U. – Mark McCarthy PhD York U. – Don Teo York U. and U. Toronto • Technical – Eoin O’Dwyer TRIUMF – Dave Morris TRIUMF – Jordan Myslik U. Toronto • Designer - DAQ, electronics – Stephen Ro U. Toronto – Mircea Cadabeschi U. Toronto – Shu Wang York U. • Mechanical engineer All now grad students or have PhD • Retired but still working for us on contract Dec 12, 2016 NSERC 2016 Review 18
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