Photodetector R&D and the Fast Focusing DIRC Prototype at SLAC: - - PDF document

▶
photodetector r d and the fast focusing dirc prototype at
SMART_READER_LITE
LIVE PREVIEW

Photodetector R&D and the Fast Focusing DIRC Prototype at SLAC: - - PDF document

Aug 10, 2023 226 likes •445 views

Photodetector R&D and the Fast Focusing DIRC Prototype at SLAC: A Status Report Blair Ratcliff, SLAC Representing C. Field, T. Hadig, D.W.G.S. Leith, G. Mazaheri, B. Ratcliff, J. Schwiening, J. Uher, J. Vavra - Motivation - R&D

slide-1
SLIDE 1

Photodetector R&D and the Fast Focusing DIRC Prototype at SLAC: A Status Report

Blair Ratcliff, SLAC

Representing

  • C. Field, T. Hadig, D.W.G.S. Leith, G. Mazaheri,
  • B. Ratcliff, J. Schwiening, J. Uher, J. Va’vra
  • Motivation
  • R&D Program Goals
  • Photon Detector Evaluation
  • Status of Prototype
  • Summary
slide-2
SLIDE 2

2

  • B. Ratcliff, Super B Factory Workshop, April 20-22, 2005
  • Need to maintain radiation length in front of

calorimeter to (<20%) at 90 degrees.

  • Radiation robustness of fused silica is OK

(expect ~0.01-1 mega-rad within 10 year lifetime).

  • Photon Detector Lifetimes must be long and be

well understood.

  • Will have good central tracking ( ~< 1 mrad in

dip angle).

  • There will be good dE/dx from the tracking

system (Is this true?).

  • Backgrounds will be a (the?) major concern.
  • Present PID performance needs to be

maintained (Does physics require that it be enhanced?).

Some PID Detector Design Assumptions and Issues:

slide-3
SLIDE 3

3

  • B. Ratcliff, Super B Factory Workshop, April 20-22, 2005

A generic DIRC device is well matched to PID needs at a Super-B Factory

SLAC group’s strategy: Since a DIRC is intrinsically a 3-D device, we should try to take full advantage of all three dimensions for best performance and background rejection. Background rejection improves ~ directly with time

  • resolution. Other uses for timing (e.g., measuring

Cherenkov photon wavelength or making PID competitive angular or TOF measurements) have resolution thresholds in the ~150 ps and ~< 100 ps range respectively.

slide-4
SLIDE 4

4

  • B. Ratcliff, Super B Factory Workshop, April 20-22, 2005

Fast Focusing DIRC detector - schematic “design”

Goal: true 3D imaging using x,y and time for each photon. The crucial issue: Is there an adequate photon detector ?? (Many questions including (1) quantum efficiency; (2) noise; (3) cross talk;(4) timing resolution; (5) geometrical considerations; (6) operation in a magnetic field; (7)

  • perational lifetime; (8) cost.
slide-5
SLIDE 5

5

  • B. Ratcliff, Super B Factory Workshop, April 20-22, 2005

Goals of R&D Program

I. Detailed Lab Investigation of Candidate Photon Detectors a. Develop methodology to study timing, efficiency and spatial properties of candidate detectors. b. Evaluate candidate detectors. c. Work with manufacturers to improve product. II. Test detector concepts and candidate photon detectors in a “conceptual” scale prototype a. ~ 400 channels of fast electronics. b. 4m fused silica bar, ~100 ps timing resolution, and spatial resolution similar to BaBar DIRC. c. Demonstrate that (1) detector methodology is understood, and (2) demonstrate correction of chromatic error by timing. d. Test and evaluate performance of photon detector candidates in a “real” detector. e. Evaluate operations issues.

slide-6
SLIDE 6

6

  • B. Ratcliff, Super B Factory Workshop, April 20-22, 2005

Hamamatsu H-8500 Flat panel MaPMT

Hamamatsu Co. data sheet

slide-7
SLIDE 7

7

  • B. Ratcliff, Super B Factory Workshop, April 20-22, 2005

Burle 85011 MCP-PMT Burle Co. data sheet

slide-8
SLIDE 8

8

  • B. Ratcliff, Super B Factory Workshop, April 20-22, 2005

Scanning setup to measure PMT response

  • Light Source
  • PiLas laser diode operating in single photoelectron mode.
  • λ = 635 & 430nm (on loan from T. Sumyioshi).
  • 63µm dia. multi-mode fiber, with lenses at both ends; ~150 µm spot;

timing resolution ~ 35 ps.

  • x-y Stage
  • Stepper motor moves the end of the fiber equipped with a lens, typical

x-step ~ 100µm & y-step ~ 1mm.

  • Data Accumulation
  • A “hit” must be in the illuminated pad within a time window
  • Efficiency is relative either to the 2 inch dia. Photonis XP 2262B PMT.

( or the DIRC PMT, ETL 9125FLB17).

  • Typical DAQ trigger rate: 20kHz.
slide-9
SLIDE 9

9

  • B. Ratcliff, Super B Factory Workshop, April 20-22, 2005

Resolution of the scanning system

Hamamatsu Flat Panel H8500 MaPMT #2 Micro-structure of the dynode electrodes:

  • Clearly see the details of the dynode electrode structure. Spatial

resolution of the system is less than 150 µm, for a step size of 25µm.

slide-10
SLIDE 10

10

  • B. Ratcliff, Super B Factory Workshop, April 20-22, 2005

Typical Scan: The Relative Spatial Response Along a Line Across 8 Pads

Hamamatsu H8500 Flat Panel-PMT #2 Burle 85011-501 MCP-PMT #3

In this example, the Hamamatsu MaPMT uniformity is ~1:2.5 and the Burle MCP-PMT uniformity is ~1:1.5.

slide-11
SLIDE 11

11

  • B. Ratcliff, Super B Factory Workshop, April 20-22, 2005

Typical MCP Photo-detector (Burle) Scans

  • Typical relative efficiency is 50-60% of the 2 inch dia. Photonis XP

2262B PMT at 430nm. The efficiency drops to 30-50% around the edges at 430nm.

635 nm: 430nm: Burle MCP- PMT #3 Burle MCP- PMT #4 Burle MCP- PMT #8 Burle MCP- PMT #10

slide-12
SLIDE 12

12

  • B. Ratcliff, Super B Factory Workshop, April 20-22, 2005

Typical Flat PMT (Hamamatsu) Scans

Hamamatsu Flat Panel MaPMT relative efficiency is 50-70% of the Photonis XP 2262B PMT at 430nm. The efficiency drops to 30-50% around the edges at 430nm. 635 nm: 430nm: Hamamatsu MaPMT #2 Hamamatsu MaPMT #1 Hamamatsu MaPMT #4

slide-13
SLIDE 13

13

  • B. Ratcliff, Super B Factory Workshop, April 20-22, 2005

Timing studies in MaPMT and MCP-PMT

  • Double Gaussian fit.
  • Hamamatsu Flat Panel MaPMT timing resolution is sufficient to

correct chromatic term.

  • Burle MCP-PMT #3 has a very long tail due to recoil electrons from the

MCP top surface (the tail contains ~20% of all events !). The MCP-to-cathode distance is 6mm.

Hamamatsu Flat Panel H8500 PMT Burle 85011-501 MCP-PMT

MCP #3 MaPMT #2

Light source: Use the 635nm PiLas laser diode in single photoelectron mode.

slide-14
SLIDE 14

14

  • B. Ratcliff, Super B Factory Workshop, April 20-22, 2005

Dependence of timing resolution on the Burle MCP PMT design

Double Gaussian fit. The reduction of the MCP-to-Cathode distance to 0.75mm limits the rate of recoiling photoelectrons from the MCP surface, which reduces the tail in the timing

  • spectrum. These electrons are, however, lost from the

detection efficiency, but the spectrum is more Gaussian.

New design (85011-430) MCP-to-Cathode distance = 0.75 mm; 8x8 pads; one pad selected Former design (85011-501 ) MCP-to-Cathode distance = 6 mm; 8x8 pads; one pad selected

MCP #16 MCP #3

Light source: Use the 635nm PiLas laser diode in single photoelectron mode.

slide-15
SLIDE 15

15

  • B. Ratcliff, Super B Factory Workshop, April 20-22, 2005

Compare timing distributions on two different pads

Single Gaussian fit to the timing distribution generated at each laser head location. Measure typically σ = 70-80ps in the central pad region, slightly worse near the boundary. Worse timing resolution around edges is due to the charge sharing which causes lower pulse height, and possibly cross-talk from hits in neighboring pads.

MCP #16, Pad 14: MCP #16, Pad 24:

slide-16
SLIDE 16

16

  • B. Ratcliff, Super B Factory Workshop, April 20-22, 2005

Focusing DIRC prototype

3D imaging: x,y, and time. Photon propagation time measured to σ ~100ps: allows timing to be used directly in separation; the correction of the chromatic error contribution to the Cherenkov angle error; and efficient background suppression. Mirror focusing: removes bar exit aperture from the angular resolution. Expected angular performance similar to present BaBar DIRC: defined by chosing focal length and pixel size (6x6 mm at present).

Calibration Fiber Detector Mirror Fused Silica bar Filled with KamLand mineral oil Focal plane

slide-17
SLIDE 17

17

  • B. Ratcliff, Super B Factory Workshop, April 20-22, 2005

Status of Photo-Detector Testing Program

  • Have developed and are utilizing a bench top system

capable of measuring spatial and timing characteristics of photodetectors to better than ~150 um in space and ~ 50 ps in time.

  • Have characterized a substantial number of candidate

PMTs, especially the Hamamatsu Flat Panel MaPMT and the Burle MCP-PMT. Are working with the manufacturers to improve performance.

  • Typical relative eff (compared to a standard PMT) at

430 nm is ~50-60% for the BURLE MCP-PMT, and ~ 60- 70% for the Hamamatsu MaPMT. The efficiency varies significantly near the edges and across pads.

  • There are still substantial non-Gaussian tails in timing
  • distributions. To be useful for the most challenging

applications, these must be reduced substantially

  • Many real world issues are still to be understood,

especially aging, and performance in a magnetic field.

  • Basic performance should allow reasonable performance

from a prototype, but there is little margin for error or efficiency loss.

  • As for the future: Is the glass ½ empty or ½ full?
slide-18
SLIDE 18

18

  • B. Ratcliff, Super B Factory Workshop, April 20-22, 2005

Elements of the prototype

Mirror 4m-long fused silica DIRC bar Detector box filled with oil Photon detectors at the focal plane

slide-19
SLIDE 19

19

  • B. Ratcliff, Super B Factory Workshop, April 20-22, 2005

The DIRC Prototype in the Test Beam

4m-long DIRC bar + Photon detector 3 MCP-PMTs and 2 MaPMTs: 320 ch. In test beam (ESA SLAC) 32-channel SLAC CFD/TAC board

slide-20
SLIDE 20

20

  • B. Ratcliff, Super B Factory Workshop, April 20-22, 2005

Focusing DIRC Prototype Electronics

  • Signals from Burle MCP-PMT #16, P/N 85011-430. PiLas laser diode is used as a

light source, and as a TDC start/stop.

  • Amplifier is based on two Elantek 2075EL chips with the overall voltage gain: ~130x,

and a rise time of ~1.5ns.

  • Constant-fraction-discriminator (CFD) analog output is available for each channel

(32 channels/board).

  • TAC circuit is based on Burr-Brown Sample/Hold SHC5320 chip.
  • 32-channel/board, VME-based, 12 bit ADC, controlled by FPGA logical array.

TAC/ADC system gives 25ps/count.

SLAC Amplifier: SLAC CFD & TAC: Detector Amplifier CFD & TAC 12 bit ADC Overall chain:

CFD analog pulse out

Amplifier outputs from MCP-PMT (trigger scope on CFD analog output), 100mV/div, 1ns/div Amplifier output from MCP-PMT (trigger on PiLas), 100mV/div, 1ns/div

slide-21
SLIDE 21

21

  • B. Ratcliff, Super B Factory Workshop, April 20-22, 2005

Summary

  • PMT development and associated testing
  • continues. Testing by interested customers

and a continuing interchange of the data and requirements with the manufacturers are essential for getting the required

  • devices. This R&D needs continuing effort.
  • Prototype is waiting for test beam in

SLAC ESA. (Hope to get some initial data very soon!)

  • Expect to measure basic DIRC

performance parameters, study PMT performance issues, and demonstrate the chromatic correction using timing.

  • Even at this “small” scale, it is a non-

trivial effort.