improved pmts for the cherenkov telescope array project razmik mirzoyan
DESCRIPTION
Improved PMTs for the Cherenkov Telescope Array project Razmik Mirzoyan for the Focal Plane Instrumentation WG Max-Planck-Institute for Physics Munich, Germany. C herenkov T elescope A rray (CTA). for Very High Energy Ground-Based -ray Astronomy. - PowerPoint PPT PresentationTRANSCRIPT
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Improved PMTs for the Cherenkov Telescope Array project
Razmik Mirzoyanfor the Focal Plane Instrumentation WG
Max-Planck-Institute for PhysicsMunich, Germany
Razmik Mirzoyan: Improved PMTs forthe CTA Project11 June 2011, TIPP-2011, Chicago, USA 1
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Cherenkov Telescope Array (CTA)
• Core people: MAGIC, H.E.S.S. and VERITAS collaborations An initiative to build the next generation large ground –based gamma ray instrument of ~10 times higher sensitivity
• 840 scientists from > 100 institutions (EU, USA and Japan)• Study distant AGNs, Black Holes, Gamma Ray Bursts, as well as the galactic sources (Pulsars,
Supernovae, µquasar,…) • from 10 GeV to 100 TeV• Answer the long-standing question about the origin of cosmic rays
• ~100 telescopes, 2-arrays (in S & N)• Site search ongoing
for Very High Energy Ground-Based -ray Astronomy
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CTA Project
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• 3 types of telescopes are planned: several large 23m, many mid-size 12m and many small ~(4-7)m• Standard sensor: PMTs (SiPM: candidate sensor)
Cherenkov Telescope Array (CTA)
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Quantum Efficiency measurements
Razmik Mirzoyan: Improved PMTs forthe CTA Project
Company Type QEpeak() <QE>Cher
Hamamatsu 86191“
28,7 ± 2,2 (390 nm)
19,4 ± 0,3
Hamamatsu 94201,5“
34,6 ± 3,1 (370 nm)
22,9 ± 0,4
Hamamatsu 77242“
38,9 ± 3,3 (370 nm)
25,7 ± 0,4
Electron Tubes
9117B1,5“
34,0 ± 3,2 (360 nm)
19,9 ± 0,3
Electron Tubes
9142B1,125“
30,2 ± 2,7 (370 nm)
16,5 ± 0,3
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Razmik Mirzoyan: Improved PMTs forthe CTA Project
1.5’ size, super-bialkali candidate PMTs
Hamamatsu R9420 modified(convex input window shape)(mat and polished input window types)
Hamamatsu R8619 modifiedBody of R9420 but used 8619 dynode system (also two window types)
Electron Tubes 9117B
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Exploit the lower AP rates of the R8619 with the high QE of the R9420 !
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1.5‘ Electron Tubes Enterprises 9117B
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11 June 2011, TIPP-2011, Chicago, USA
Razmik Mirzoyan: Improved PMTs forthe CTA Project
1.5’ PMT Hamamatsu R9420, predecessor of the current R11920-100-10
Simulated ph.e. angular distribution~ cos()= 400 nmSingle ph.e.
Development goal: improve the QE but also optimise the ph.e. Collection EfficiencyThe product of QE x Collection Efficiency is the Photon Detection Efficiency optimise the TTS
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The measured QE of the 1.5´CTA target PMT from Hamamatsu
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Afterpulse Rate measurements
Razmik Mirzoyan: Improved PMTs forthe CTA Project
• Single Photoelectron measurement estimate F-factor and Gain, evaluate amplitude of pulses• AP data taking: record 20 µs long FADC trace after main pulse (2 GHz sampling rate), 60000 events per HV for 5 to 30 phe pulse amplitude
• offline Analysis of recorded data: AP Arrival time, Pulse shapes and rates
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Single photoelectron measurement
Razmik Mirzoyan: Improved PMTs forthe CTA Project
1.5 ” Hamamatsu 9420 MODP:
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Target Hamamatsu PMT operated at a HV 900 V, gain ~ 40k
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Razmik Mirzoyan: Improved PMTs forthe CTA Project
A n amplifier providing 5000e- equivalent noise/10ns (developed in Univ. Barcelona) has been used for this measurement
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Afterpulsing Rates new and comparable old PMTs
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Afterpulsing Rates
Razmik Mirzoyan: Improved PMTs forthe CTA Project
Type AP Rate ≥ 4ph.e. [%]
Hamamatsu 9420 Old 0.3
Hamamatsu 9420 MODF XA7038 New 0.15
Hamamatsu 8619 MODP XA7043(Body of 9420)
New 0.032
Hamamatsu 8619 Old 0.0085
ET enterprize 9142B 0.005
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Razmik Mirzoyan: Improved PMTs forthe CTA Project
Pulse shape – Timing measurementCompany PMT
serialWindow -Type Max applied HV FWHM [ns]
Hamamatsu 9420ZP0753
Flat/concave, 1,5 ” 1200 V 2,35
Hamamatsu 9420MODF_XA7038
Flat/concave, 1,5 ” 1100 V 2,42
Hamamatsu 8619DV2520
Flat/concave, 1 “ 900 V 3,10
Hamamatsu 8619MODP_XA7043
Flat/concave, 1,5 ” 1100 V 2,86
Electron Tubes 9117B_477 Hemispherical, 1,5 ” 1100 V 1,53
Electron Tubes 9142B_10011 Flat/concave,1,125” 600 V 3,63
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Pulse shape
Razmik Mirzoyan: Improved PMTs forthe CTA Project
Hamamatsu 9420
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Razmik Mirzoyan: Improved PMTs forthe CTA Project
Electron Tubes 9117B
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Pulse shape
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Razmik Mirzoyan: Improved PMTs forthe CTA Project
Pulse width dependence on the applied HV
Supply voltage [V]
2,00
2,20
2,40
2,60
2,80
3,00
3,20
600 800 1000 1200
e.g. : Hamamatsu 9420
preliminary
Voltage FWHM [ns]
700 3,11
800 2,82
900 2,60
1000 2,64
1100 2,52
1200 2,35
~82/sqrt(HV)
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Razmik Mirzoyan: Improved PMTs forthe CTA Project
• AP arrival time to check, what are the sources for AP inside PMT• Peaks locate ions (H+,He+,2+, CH4
+)• Exponentially decreasing in time caused by rest gases (low”clean” vacuum)• ET tube (first picture) has very low AP with little peaks
AP sourcesVaries for different PMTs !
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Razmik Mirzoyan: Improved PMTs forthe CTA Project
Apply different voltages to a selected PMT; intensity of the laser pulses kept constant
AP rates raise with HV
Ion travel time decrease
Heavy ion focusing increases with HV
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Razmik Mirzoyan: Improved PMTs forthe CTA Project
PMT Glowing
lower left photo: seen from topLower right photo: towel around the PMT light emission from the side also visible
top right photo: glowing seen from side
Clara CCD 10 min exposure timeFilter in front to suppress the 405 nm laser lightHigh voltage, high laser intensity
We checked: all these photos show a fluorescent light emission with spectrum > 700 nm
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Razmik Mirzoyan: Improved PMTs forthe CTA Project
Right top: overlay of both lower photosLeft bottom: simple photo of the PMTRight bottom: dark measurement (PMT Glowing)
PMT Glowing
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Optical photo Exposure in dark: PMT emits light
Overlay of optical and dark exposure photos
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Razmik Mirzoyan: Improved PMTs forthe CTA Project
Summary
PMT <QE>: is approaching ~35 % in peak, folded with Cherenkov:spectrum > 20%• AP rate: achieved ≤ 0.05 % ≥ 4 Phe; Goal: ≤ 0.02 % (Ham.)• Pulse width: ~ 2.5 – 3 ns• Photo electron collection efficiency equally important as QE: optimise the PMT input window shape and curvature (bothHam. and ETE are working on it)• Both Hamamatsu and ETE are on the way of developing the best ever PMTs for the CTA project
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Razmik Mirzoyan: Improved PMTs forthe CTA Project
Thank you for your attention !
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