TORCH – a Cherenkov based Time-of-Flight DetectorEuan N. Cowieon behalf of the TORCH collaboration
E N Cowie - TORCH - TIPP 2014 1
05 June 2014
Outline
• TORCH Design and Principles.• Suitability for use in LHCb.
• MCP Requirements.• Results and simulation work.
• Electronics.• Test-Beam plans and Preparation.
E N Cowie - TORCH - TIPP 2014 2
05 June 2014
Time Of internally Reflected Cherenkov
E N Cowie - TORCH - TIPP 2014
The basics of the TORCH design
3
05 June 2014
• TORCH aims to achieve 10-15ps timing over large areas.
• Utilises Cherenkov light for fast signal production.
• Focussing optics along edges couple light to photodetectors.
5m
6m
TORCH in LHCb
E N Cowie - TORCH - TIPP 2014
pp
10 – 300 mrad
LHCb showing potential locations for TORCH [1]
4
05 June 2014
See:The RICH detector of the LHCb experimentAntonis PapanestisSession 2a) Experiments and Upgrades
Motivation
E N Cowie - TORCH - TIPP 2014 5
05 June 2014
π-K ToF difference as a function of particle momentum
• TORCH will be used in conjunction with RICH 1 & 2.
• Covers momentum region up to 10GeV/c.
• Pion-Kaon time-of-flight difference ~35ps over 9.5m.
• 3-σ separation 10-15 ps.
• ~30 photons detected per track gives requirement of 70ps per photon.
Focussing
E N Cowie - TORCH - TIPP 2014
Schematic of focussing optics
6
05 June 2014
• Converts photon propagation angle into position on focal plane.
• Photodetector is split into 128 pixels, with resolution ~1mrad.
• Accounts for uncertainty in photon emission position through plate.
• Covers angles from 0.45rad to 0.85rad.
Photon Detection
E N Cowie - TORCH - TIPP 2014
Required granularity of the final TORCH MCP.
7
05 June 2014
Development of MCP-PMTs underway.
Final device requires:
1. Stable gain performance up to least 5C/cm2.
2. Granularity equivalent to 8x128 pixels.• Proposed device has 64x64 pixels.
• Nearest neighbour charge sharing in fine granularity direction.
• Pixels ganged together in coarse granularity direction.
3. 60 mm pitch with 53x53mm2 active area.
Photon Detection
E N Cowie - TORCH - TIPP 2014
Required granularity of the final TORCH MCP.
8
05 June 2014
Three phases of development by Photek:
1. Long lifetime ALD coated single channel.• Currently under study.
2. High granularity devices.• Pixel size and pitch matching
final device.
3. Full prototype.• Full size and pitch, high
granularity, long lifetime.
MCP-PMT Lifetime
E N Cowie - TORCH - TIPP 2014
Photocathode response as a function of collected charge [2].
9
05 June 2014
Coated (improved) MCP-PMT Uncoated MCP-PMT
TORCH Minimum Requirement
MCP-PMT Simulation
E N Cowie - TORCH - TIPP 2014
Simulated uncertainty on position using charge-sharing as a function of gain and electronics threshold.
10
05 June 2014
• Extra granularity achieved with charge sharing.
• Uncertainty in reconstructed position depends on gain and electronics threshold.
• For more information see poster: Simulation studies of a novel, charge sharing, multi-anode MCP detector. Thomas Conneely & James Milnes, Photek LTD.
Ele
ctro
nics
Thr
esho
ld (
fC)
Gain ( electrons)
Timing
E N Cowie - TORCH - TIPP 2014
σpmt = 23ps
𝜎 𝑡𝑜𝑡𝑎𝑙=𝜎 𝑝𝑚𝑡=23𝑝𝑠Phase 1 MCP-PMT timing distribution.
11
05 June 2014
0 200 400 600 800 1000 1200 14001
10
100
1000
10000
Time [ps]
Co
un
ts
Timing smear divided into three categories:
1. Contributions arising from the PMT.
Timing
E N Cowie - TORCH - TIPP 2014
𝜎 𝑡𝑜𝑡𝑎𝑙=√𝜎𝑝𝑚𝑡2 +𝜎𝑜𝑝𝑡𝑖𝑐𝑠
2 60𝑝𝑠
σopt = 55ps
Simulated optics timing distribution.
12
05 June 2014
Timing smear divided into three categories:
1. Contributions arising from the PMT.
2. Contributions arising from the optics.
Timing
E N Cowie - TORCH - TIPP 2014
𝜎 𝑡𝑜𝑡𝑎𝑙=√𝜎2𝑝𝑚𝑡❑ +𝜎❑
2𝑜𝑝𝑡+𝜎❑
2𝑒𝑙𝑒𝑐 70𝑝𝑠
13
05 June 2014
Timing smear divided into three categories:
1. Contributions arising from the optics.
2. Contributions arising from the PMT.
3. Contributions arising from the Electronics.
NINO leading edge jitter [3].
HPTDC timing resolution [4].
Electronics
E N Cowie - TORCH - TIPP 2014
• Initial tests of Nino8 and HPTDC show intrinsic resolution of 40ps [5].
• R&D into electronics using 32 Channel NINO chips with HPTDC underway.
14
05 June 2014
Nino8HPTDC
Nino32
E N Cowie - TORCH - TIPP 2014
Fused Silica
MCP-PMTs
Test-Beam
15
05 June 2014
Focussing Surface
• Radiator plate measuring 350x120x10 mm3 joined to a focussing block.
• Read out by two MCP-PMTs on the focal plane.
• Aiming for December deployment at T9 beam on the PS at CERN.
Future Work• Phase 1 MCP-PMTs continue to be tested.
• Phase 2 MCP-PMTs delivered this year.• Phase 3 to follow next year.
• A prototype module will be developed to prove the full concept.
• Proposal will be submitted to LHCb upon successful completion of R&D phase.
E N Cowie - TORCH - TIPP 2014 16
05 June 2014
FinThanks for listening!
E N Cowie - TORCH - TIPP 2014 17
05 June 2014
References[1] The LHCb Collaboration, “Letter of Intent for the LHCb Upgrade”, CERN-LHCC-2011-001, 29 March 2011 (v2).
[2] T. M. Conneely, J. S. Milnes, J. Howorth, Nuclear Instruments and Methods in Physics Research A 732 (2013) 388-391.
[3] M. Despeisse et al. IEEE TRANSACTIONS ON NUCLEAR SCIENCE, VOL. 58, NO. 1, FEBRUARY 2011
[4] J. Christiansen, “High Performance Time to Digital Converter”, CERN/EP-MIC, 2002.
[5] R Gao et al, 2014 JINST 9 C02025.
E N Cowie - TORCH - TIPP 2014 18
05 June 2014
Extra Slides
E N Cowie - TORCH - TIPP 2014 19
05 June 2014
Start Time
E N Cowie - TORCH - TIPP 2014 20
Example from PV of same event After removing outliers
ps
05 June 2014
Modular Design
E N Cowie - TORCH - TIPP 2014 21
05 June 2014
A modular design for TORCH
Effects of Modular Design
E N Cowie - TORCH - TIPP 2014 22
05 June 2014
Moduleconsidered
Without dispersion or
reflection off lower edge
Including dispersion and
reflection off lower edge
Dispersion
E N Cowie - TORCH - TIPP 2014 23
05 June 2014
𝑐𝑜𝑠𝜃𝑐=1
𝛽𝑛❑
𝑛❑=1
𝛽cos𝜃𝑐
Wavelength (nm)
n
𝑛𝑔𝑟𝑜𝑢𝑝=𝑛− 𝜆0𝑑𝑛𝑑𝜆
Photon production spectrumWavelength dependence of refractive indexes
Performance
E N Cowie - TORCH - TIPP 2014 24
05 June 2014
Correct ID
Mis-ID
Correct ID
Mis-ID
Kaon ID performancePion ID performance
Photon Detection
E N Cowie - TORCH - TIPP 2014
Faceplate
Photocathode
Dual MCP
Anode
Gain ~ 106
photoelectron V ~ 200V
V ~ 200V
V ~ 2000V
photon
Faceplate
Photocathode
Dual MCP
Anode
Gain ~ 106
photoelectron V ~ 200V
V ~ 200V
V ~ 2000V
photon
Example of MCP internal layout
25
05 June 2014
• Photodetectors required to have precise single photoelectron time resolution and long lifetime
• MCP-PMTs chosen for lower intrinsic transit-time spread.
• Atomic Layer Deposition coating will be used to increase lifetime.