Blair Ratcliff5 th SuperB Workshop, Paris May 2007 1 PID Related R&D at SLAC: The Focusing DIRC and...

Blair Ratcliff5th SuperB Workshop, Paris May 20071

PID Related R&D at SLAC: PID Related R&D at SLAC: The Focusing DIRC and a The Focusing DIRC and a

Fast TOF Using Cherenkov Fast TOF Using Cherenkov Light. Light.

Blair RatcliffBlair Ratcliff

Representing: I. Bedajanek, J Benitez, D.W.G.S. Leith, G. Mazaheri, J. Schwiening, K. Suzuki, J. Uher, J. Va’vra.


Focusing DIRC Prototype GoalsFocusing DIRC Prototype GoalsWork with manufacturers to develop and characterize one or more fast, pixelated photon detectors including;

• basic issues such as cross talk, tube lifetime, and absolute efficiency• operation in 15 KG field

Measure single photon Cherenkov angular resolution in a test beam• use a prototype with a small expansion region and mirror focusing, instrumented with a

a number of candidate pixelated photon detectors and fast (25 ps) timing electronics Much lower background sensitivity with somewhat improved performance parameters • demonstrate correction of chromatic production error via precise single photon timing• demonstrate that the performance with mirror focusing is as expected.• measure N0 and timing performance of candidate detectors.


Focusing DIRC Prototype OpticsFocusing DIRC Prototype Optics

Radiator• 3.7m-long bar made from three spare high-quality

BABAR-DIRC barsExpansion region

• coupled to radiator bar with small fused silica block• filled with mineral oil (KamLand experiment) to match

fused silica refractive index • include optical fiber for electronics calibration• would ultimately like to used solid fused silica block

Focusing optics• spherical mirror from SLD-CRID detector (focal length 49.2cm)

Photon detector• placed in fixed slots allowing easy replacement.• typically using 2 Hamamatsu flat panel PMTs and 3 Burle MCP-PMTs in focal plane• readout to CAMAC/VME electronics with 25 ps resolution. Limited number of channels available.


Focusing DIRC prototype photon Focusing DIRC prototype photon detectorsdetectors

Nucl.Inst.&Meth., A 553 (2005) 96Nucl.Inst.&Meth., A 553 (2005) 96

TTiming iming resolutions resolutions were were obtained obtained using a fast using a fast laser diode laser diode in bench in bench tests with tests with single single photons on photons on pad center.pad center.

narrow ≈70ps

time (ns)

narrow ≈140ps

time (ns)

narrow ≈220ps

time (ns)

1) Burle 85011-501 MCP-PMT (64 pixels, 6x6mm pad, TTS ~50-70ps)

2) Hamamatsu H-8500 MaPMT (64 pixels, 6x6mm pad, TTS ~140ps)

3) Hamamatsu H-9500 Flat Panel MaPMT (256 pixels, 3x12mm pad, TTS ~220ps)


Beam Test SetupBeam Test Setup• 10 GeV/c e- beam in End Station A at SLAC.

• Beam enters bar at 90º angle.

• 10 Hz pulse rate, approx. 0.1 particle per pulse

• Bar contained in aluminum support structure

• Beam enters through thin aluminum foil windows

• Bar can be moved along long bar axis to measure photon propagation time for various track positions

• Trigger signal provided by accelerator

• Fiber hodoscope (16+16 channels, 2mm pitch) measures2D beam position and track multiplicity

• Cherenkov counter and scintillator measure event time

• Lead glass calorimeter selects single electrons

Mirror and oil-filled detector box:Movable bar support and hodoscope Start counters, lead glass

Hodoscope

Scintillator

Cherenkovcounter

Calorimeter

Radiator bar in support structure

Prototype

e– beam


10 GeV/c electron beam 10 GeV/c electron beam data.data.

~ 200 pixels ~ 200 pixels instrumented.instrumented.

Ring image is most Ring image is most narrow in the 3 x 12 mm narrow in the 3 x 12 mm pixel detector.pixel detector.

Hamamatsu H-8500 Hamamatsu H-9500 Burle 85011-501 Burle 85011-501

Burle 85011-501Burle 85011-501

Cherenkov ring in pixel domain:

Cherenkov photons in time domain:

Cherenkov Photons In Time & Pixel DomainsCherenkov Photons In Time & Pixel Domains


Cherenkov angle production Cherenkov angle production controlled by controlled by nnphasephase (cos (cos cc = 1/(n = 1/(nphasephase:: c c (red)(red) < < c c (blue)(blue)Propagation of photons Propagation of photons is controlled by is controlled by nngroupgroup (v(vgroupgroup = = cc0 0 /n/ngroupgroup = c = c0 0 /[n/[nphasephase - - phasephase):): vvgroupgroup(red)(red) > > vvgroup group (blue)(blue)

Principle ofchromaticcorrectionby timing:

TOP = time ofpropagationof photonin the bar

TOP/Lpath = 1/vgroup()

The DIRC as a SpectrometerThe DIRC as a Spectrometer


ll detectors: PMT with 3mm pixels only:

Structure in the Structure in the uncorrecteduncorrected distributions are caused by the coarse pixelization and the finite distributions are caused by the coarse pixelization and the finite beam phase space. The time correction smears this effect away. beam phase space. The time correction smears this effect away.

Smaller radial pixel size (3mm) helps to improve the Cherenkov angle resolution as expected.Smaller radial pixel size (3mm) helps to improve the Cherenkov angle resolution as expected.

Correction off: Correction off:Correction on:

~ 5.0 mrad

~ 5.1 mrad

Chrom

+Pixel

Correction off: Correction off:Correction on:Correction on:

~ 5.0 mrad

~ 5.1 mrad

Chrom

+Pixel

Resolution Improvement with Chromatic CorrectionResolution Improvement with Chromatic Correction


Main contributions to the Main contributions to the cc resolution:resolution:

- - chromatic smearingchromatic smearing: : ~ 3-4 mrad~ 3-4 mrad

- - 6mm pixel size6mm pixel size: : ~5.5 mrad~5.5 mrad

- - optical aberrations of this particular designoptical aberrations of this particular design: : grows from 0 mrad at ring center to 9 mrad in outer wings of Cherenkov ringgrows from 0 mrad at ring center to 9 mrad in outer wings of Cherenkov ring

c resolution - all pixels: c resolution - 3mm pixels only:

Data / GEANT 4 MC ComparisonData / GEANT 4 MC Comparison


Prototype’s Prototype’s Npe_measured Npe_measured andand Npe_expected Npe_expected are consistent are consistent withinwithin ~20%. ~20%.

Hamamatsu H-9500 Hamamatsu H-9500 MaPMTsMaPMTs: :

We expectWe expect No No ~ 31 cm~ 31 cm-1-1, which , which in turn givesin turn gives Npe ~ 28 Npe ~ 28 for 1.7 for 1.7 cm fused silica bar thickness, cm fused silica bar thickness, and somewhat better and somewhat better performance in performance in pi/Kpi/K separation separation than the present BaBar DIRC. than the present BaBar DIRC.

Burle-Photonis MCP-PMT:Burle-Photonis MCP-PMT:

We expect We expect NoNo ~ 22 cm~ 22 cm-1-1 and and Npe ~ 20Npe ~ 20 for B = 0kG. for B = 0kG.

BaBar DIRC designBaBar DIRC design: :

NoNo ~ 30 cm~ 30 cm-1-1, and, and Npe ~ 27 Npe ~ 27..

Expected performance of a final device:

Focusing DIRC prototype bandwidth:

Performance Estimates of this Design for Different PMT Performance Estimates of this Design for Different PMT Choices (JV model)Choices (JV model)


- Goal: Develop a Cherenkov Based TOF with total timing resolution <~15 ps.

Bench Tests of Main Elements of a Fast TOFBench Tests of Main Elements of a Fast TOF


Laser Test Stand Laser Test Stand

5-m long fiber

Detector

Lens + collimator

Lens + collimator

Laser diode

Control unit

PiLas

1.5-meter longcable

Start

x & y stage +rotation

PiLas laser head:

ParameterParameter SLAC testsSLAC tests

Laser diode sourceLaser diode source PiLasPiLas

WavelengthWavelength 635 nm635 nm

TTS light spread (FWHM)TTS light spread (FWHM) ~ 35 ps~ 35 ps

Fiber sizeFiber size 62.5 62.5 mm

Start

Calibration of a fast detector:


Single Photon Timing Resolution (Single Photon Timing Resolution (TTSTTS))

10 10 m MCP hole diameterm MCP hole diameter B = 0 kGB = 0 kG 64 pixel devices, pad size: 6 mm x 6 mm.64 pixel devices, pad size: 6 mm x 6 mm. Phillips CFDPhillips CFD PiLas red laser diode operating in the PiLas red laser diode operating in the

single photoelectron mode (635 nm).single photoelectron mode (635 nm). TTS TTS < < (32 (3222-15-1522-11-1122) = 26 ps (Npe = ) = 26 ps (Npe =

1)1)

Ortec VT120A amplifier ~0.4 GHz BW, 200x gain + 6dB

Fit: g + g

Burle/Photonis MCP-PMT 85012-501 (ground all pads except one)

Fit: g + g

Hamamatsu C5594-44 amplifier 1.5 GHz BW, 63x gain


Bench Tests With Fast Time DigitizationBench Tests With Fast Time Digitization

Detector

Laser diode

Control unit

PiLas

PiLas ~15 ps/Npe

Trigger

TTL

NIM

Disc

PiLas_trigger ~?

Pulser

START

STOP

14 bitADC 114

TAC 566

Pulser + TAC_ADC ~ 3.2 ps

(My measurement)

Fiber ~?

Delay ~?

MCP-PMT

= {MCP-PMT+

Fiber + Amp_CFD +

Delay +

PiLas + Pulser+TAC_ADC +

PiLas_trigger}

+ Systematic effects: laser & temperature drifts, ground loops, etc.

Pulser_TAC_ADC

~ 3.2 ps

Ortec 9236 Amp/CFD

Amp_CFD ~ 6 -7 ps (Manufacturer)

Manufacturer My measurement


Timing Resolution Versus Npe for different R/OTiming Resolution Versus Npe for different R/O

Npe = 50-60 for 1cm-thick Quartz radiator + window & with Burle Bialkali Npe = 50-60 for 1cm-thick Quartz radiator + window & with Burle Bialkali QE.QE.

< 15 ps seems feasible.< 15 ps seems feasible. The Ortec 9327-like performance is adequate. The Ortec 9327-like performance is adequate.


SummarySummary Pixelated Photon detectors continue to be improved by manufacturers. The performance

expected from a small SOB DIRC with a MaPMT H-9500 tube should be similar to the BaBar DIRC in Npe with ~ 20% better resolution with the 3 mm pixels. Need to continue to work with manufactures in order to improve the photon detectors.

We have demonstrated the principle of chromatic correction to the Cherenkov angle using timing.

Bench tests of fast timing PMTs are encouraging to date. Best results with the laser diode:Best results with the laser diode:

- - ~ ~ 12 ps for Npe = 50-60 (as expected from 1cm thick Cherenkov radiator)12 ps for Npe = 50-60 (as expected from 1cm thick Cherenkov radiator)..

- - TTS TTS < 26 ps for Npe ~ 1< 26 ps for Npe ~ 1..- - Upper limit on the MCP-PMT contributionUpper limit on the MCP-PMT contribution: : MCP-PMT MCP-PMT < 6.5 ps< 6.5 ps..

- - TAC/ADC contribution to timingTAC/ADC contribution to timing:: TAC_ADC TAC_ADC < 3.2 ps< 3.2 ps..

- - Total electronics contribution at present:Total electronics contribution at present: Total_electronicsTotal_electronics~ 7.2 ps~ 7.2 ps..

More to come soon….We hope to continue Fast DIRC detector work and confirm TOF performance in a test beam run this year….However, the future of test beams at SLAC is quite uncertain.


Burle 85011-501 MCP-PMT• bialkali photocathode• 25μm pore MCP• gain ~5×105

• timing resolution ~70ps• 64 pixels (8×8), 6.5mm pitch

Typical Scanning System results Typical Scanning System results (Burle 85011-501)(Burle 85011-501)


Typical Scanning System Results Typical Scanning System Results (Hamamatsu H-8500)(Hamamatsu H-8500)

Hamamatsu H-8500 Flat Panel Multianode PMT• bialkali photocathode• 12 stage metal channel dynode• gain ~106

• timing resolution ~140ps• 64 pixels (8×8), 6.1mm pitch


Timing versus Beam PositionTiming versus Beam Position

Hit time distribution for single PMT pixel in three positions. Position 1

direct

mirrorreflection

Position 4

Position 6

hit time (ns)Mirror

Expansion region

Position 1

Position 4

Position 6


Chromatic BroadeningChromatic Broadening

ΔTOP (ns)

ΔTOP (ns)

hit time (ns)

Example: chromatic growth for one selected detector pixel in position 1

75cm path

870cmpath

σnarrow≈170ps

σnarrow≈420ps

• First peak ~75cm photon path length

• Second peak ~870cm photon path length

• Important: careful calibration of all TDCchannels to translate counts into ps

• Use accelerator trigger signal as event time

• Calculate the time of propagation assuming average <λ>≈410nm

• Plot ΔTOP: measured minus expected time of propagation

• Fit to double-Gaussian

• Observe clear broadening of timing peak for mirror-reflected photons

calculate from reco


Burle MCP-PMT with 10 micron holes: sensitivity to magnetic field angular rotation

wrt z axis ( B = 15kG)


Hamamatsu H-9500Hamamatsu H-9500

Hamamatsu H-9500 Flat Panel Multianode PMT• bialkali photocathode• 12 stage metal channel dynode• gain ~106

• typical timing resolution ~220ps

• 256 pixels (16×16), 3 mm pitch• custom readout board – read out as 4×16 channels

σnarrow ≈220ps

Efficiency relative to Photonis PMT, 440nm, H-9500 at -1000V


Timing in Magnetic Field Timing in Magnetic Field (B=15 Kg)(B=15 Kg)


Chromatic EffectsChromatic Effects

Chromatic effect at Cherenkov photon production cos c = 1/n(λ)

n(λ) refractive (phase) index of fused silica n=1.49…1.46 for photons observed in BABAR-DIRC (300…650nm)

→ cγ = 835…815mrad

Larger Cherenkov angle at production results in shorter photon path length

→ 10-20cm path effect for BABAR-DIRC (UV photons shorter path)

Chromatic time dispersion during photon propagation in radiator bar

Photons propagate in dispersive medium with group index ng

for fused silica: n / ng = 0.95…0.99

Chromatic variation of ng results in time-of-propagation (ΔTOP) variation

ΔTOP= | –L d/ c0 · d2n/d2 |

(L: photon path, dwavelength bandwidth)

→ 1-3ns ΔTOP effect for BABAR-DIRC (net effect: UV photons arrive later)

Refractive Indices and Dispersion versus Wavelength for SiO2

1.4

1.5

1.6

1.7

1.8

1.9

2

0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7

Photon Wavelength (microns)

Refra

ctiv

e In

dex

0.01

0.1

1

10

Disp

ersi

on, -

dn/d

n(phase) n (group)

Dispersion [n (phase)] Dispersion [n (group)]

Dispersion [n (group)]/ Dispersion [n (phase)]


ReconstructionReconstruction

Precisely measured detector pixel coordinates and beam parameters.→ Pixel with hit (xdet, ydet, thit) defines 3D propagation vector in bar

and Cherenkov photon properties (assuming average ) x, y, cos cos cos Lpath, nbounces, c, c , tpropagation


PID Software R&D Studies are NeededPID Software R&D Studies are Needed

• Need high quality physics MC simulations to demonstrate need for detector upgrades base-lined. (Realism is important , not only for PID simulation (both ID and Mis-ID rates), but also for interactions in material, tracking, CAL performance, etc.)

• Will need to be able to study physics tradeoffs between an added PID device and other detector systems.

• Is a separate system necessary or should dE/dx be revisited?

• Need specific physics channels that demonstrate compelling need for forward PID.

• Geometrical coverage plus momentum range: In particular, are there important physics channels that would benefit from enhanced PID momentum coverage range?

Blair Ratcliff5 th SuperB Workshop, Paris May 2007 1 PID Related R&D at SLAC: The Focusing DIRC and...

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