1. TORCH – a Cherenkov based Time-of-Flight Detector
21 November 2018
TORCH – a Cherenkov based Time-of-Flight Detector
Euan N. Cowie
on behalf of the TORCH collaboration

2. Time Of internally Reflected Cherenkov
21 November 2018
Time Of internally Reflected Cherenkov
The basics of the TORCH design
TORCH - E N Cowie

3. TORCH in LHCb p 10 – 300 mrad 21 November 2018 TORCH - E N Cowie
LHCb showing potential locations for TORCH
TORCH - E N Cowie

4. Motivation 21 November 2018 TORCH - E N Cowie
PID Performance of TORCH alongside RICH detectors
TORCH - E N Cowie

5. Motivation σ~10-15ps per track 21 November 2018 TORCH - E N Cowie
ToF difference as a function of particle momentum
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6. Modular Design 21 November 2018 TORCH - E N Cowie
A modular design for TORCH
TORCH - E N Cowie

7. Dispersion 𝑐𝑜𝑠 𝜃 𝑐 = 1 𝛽 𝑛 𝑛 = 1 𝛽 cos 𝜃 𝑐 𝑛 𝑔𝑟𝑜𝑢𝑝 =𝑛− 𝜆 0 𝑑𝑛 𝑑𝜆
21 November 2018
Dispersion n
𝑐𝑜𝑠 𝜃 𝑐 = 1 𝛽 𝑛
𝑛 = 1 𝛽 cos 𝜃 𝑐
𝑛 𝑔𝑟𝑜𝑢𝑝 =𝑛− 𝜆 0 𝑑𝑛 𝑑𝜆
Wavelength (nm)
Wavelength dependence of refractive indexes
Photon production spectrum
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8. Focussing 128 Pixels ~1 mrad 21 November 2018 TORCH - E N Cowie
Schematic of focussing optics
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9. Focussing Quality qz vs. r θ= 0.7528 + 0.00749 r – 2.22×10-6 r2
21 November 2018
Focussing Quality
qz vs. r
θ= r – 2.22×10-6 r2
TORCH - E N Cowie

10. Photon Detection 21 November 2018 TORCH - E N Cowie
Example of MCP internal layout
Schematic of the proposed TORCH MCP
TORCH - E N Cowie

11. Timing σopt = 55ps σpmt = 23ps 𝜎 𝑡𝑜𝑡𝑎𝑙 = 𝜎 2 𝑝𝑚𝑡 + 𝜎 2 𝑜𝑝𝑡 ~60𝑝𝑠
21 November 2018
Timing
σopt = 55ps
σpmt = 23ps
MCP timing spectrum
Optics timing spectrum
𝜎 𝑡𝑜𝑡𝑎𝑙 = 𝜎 2 𝑝𝑚𝑡 + 𝜎 2 𝑜𝑝𝑡 ~60𝑝𝑠
TORCH - E N Cowie

12. Performance 21 November 2018 TORCH - E N Cowie Pion ID performance
Correct ID
Mis-ID
Correct ID
Mis-ID
Pion ID performance
Kaon ID performance
TORCH - E N Cowie

13. Conclusions TORCH is a novel combination of DIRC and ToF.
21 November 2018
Conclusions
TORCH is a novel combination of DIRC and ToF.
Designed for LHCb but principle can be adapted.
Target is ps pre track, < 70 ps per photon.
R&D project for MCP is ongoing.
TORCH - E N Cowie

14. Viewpoint angles: θ=270° φ=0°
21 November 2018
Viewpoint angles: θ=270° φ=0°
Thank you for Listening
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15. 21 November 2018
SPARES
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16. 21 November 2018
ToF β
ALICE ToF β measurements
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17. 21 November 2018
Reconstruction
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18. Start Time Example from PV of same event After removing outliers
21 November 2018
Start Time
Example from PV of same event
After removing outliers
𝜎 𝑡 0 = ps
TORCH - E N Cowie

19. Take all particles from one Primary Vertex
21 November 2018
Take all particles from one Primary Vertex
Invert PID logic, assume pions. Any outliers are then removed.
Combining information can achieve ~ few ps resolution
TORCH - E N Cowie

20. 21 November 2018
Simulation Output
TORCH - E N Cowie

21. Simulation Output Factor # photons None 254 Mirror 193 +CE 126
21 November 2018
Simulation Output
Factor # photons
None 254
Mirror 193
+CE 126
+QE 26.3
+Epotek
TORCH - E N Cowie

22. Simulation Output Factor # photons None 139 Mirror 109 +CE 70.9
21 November 2018
Simulation Output
Factor # photons
None 139
Mirror 109
+CE 70.9
+QE 14.4
+Epotek 7.03
TORCH - E N Cowie

23. 21 November 2018
Simulation Output
TORCH - E N Cowie

24. Effects of Modular Design
21 November 2018
Effects of Modular Design
Module considered
Without dispersion or
reflection off lower edge
Including dispersion and reflection off lower edge
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25. 21 November 2018
MCP Development
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26. 21 November 2018
Bristol Test Stand
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27. 06 March 2014
Diode
σ~4.25 ps
TORCH Meeting, Oxford, March 2014

28. 06 March 2014
30%
σ~41.6 ps
TORCH Meeting, Oxford, March 2014