Department of Physics Tohoku University Hiroki Kanda

Department of Physics Tohoku University

Hiroki Kanda

Tagged photon beam for the NKS2 at ELPH Tohoku Univ.

Upgrade of the STB Tagger MPPC for scintillation counters Counter Unit with an amplifier Test results Outlook for its use as an gamma ray detector Summary

9 Mar. 2015 H. Kanda @ ELPH workshop C010 2

Internal tagger Photon radiation via bremsstrahlung:

movable radiation target (carbon fiber) Bending magnet:

momentum analysis of post-bremsstrahlung electrons

Electron detectors: Energy tagging of photons Eγ = Ee – Ee’

New BST Tagger Upgrade of the STB Tagger Eγ : 0.8 – 1.27 GeV @ Ee = 1.3 GeV Energy step: 1 – 6 MeV/ ch Typical tagging rate: 2 – 3 MHz

Tagging efficiency: 𝑁𝛾𝑁𝑒

∼ 70 % @ Ee = 1.3 GeV


• Kaon photoproduction o 𝛾𝛾 → 𝐾0Λ𝑝, 𝛾𝛾 → 𝐾+Λ𝑛

o Excitation function for higher photon energy

• Double pion photopdocution o 𝛾𝛾 → 𝜋+𝜋−𝑝𝑛, 𝛾𝛾 → 𝜋+𝜋−𝛾


Photon absorption on the proton

upgraded Tagger

STB Tagger

VDC

CDC IH

OH

EV

Target

• Dipole magnet (𝐵 ~ 0.42 T, 𝐿𝑔𝑔𝑔 = 680 mm)

• Liquid deuterium target • Hodoscopes (IH and OH) • MWDC’s (CDC and SDC) • Electron veto (EV) • Geometrical acceptance

(~ 1𝜋 sr)


Bending magnet BM4

Electron detectors 40 Units

Ee = 1.3 GeV electron

Carbon radiator


Compact size for a fine grained counters 3 x 3 mm2 scintillator ⟺ 3 x 3 mm2 active area :

Hamamatsu MPPC S10931-100P (100 µm pixel size) 15 x 10 mm2 scintillator ⟺ 12.6 x12.6 mm2 active area

Hamamatsu monolithic MPPC array S11828-3344M(X1) (50 µm square pixels)

Working under a magnetic field High Quantum Efficiency: up to 50 %

(S10931-050 with cross talks and after pulses)

Low cost ($300 for ½” active area) Reasonable time resolution: 500 – 600 ps

(FWHM) Comparable to NKS2 counter systems 140 ps (Gaussian fitted σ) for TOF start counter 260 ps (Gaussian fitted σ) for TOF stop counter

S10931-100P

S11828-3344M(X1)

Hamamatsu SMD package MPPC


Position: TagF

MPPC array (S11828-3344M(X1))

MPPC ×4 (S10931-100P)

Timing: TagB

EASIROC Supplied by LAL

Dedicated readout circuit

Parallel connection

Capacitance coupling


Reflective painted scintillator prism: BC404 3x3x24 mm3 for TagF 15x10x20 mm3 for TagB

Production by Fujidiamond International

g

Photo-Detector Board

Parallel connection of all the channels of monolithic MPPC array Increase of the dark count rate

High pass filter Reduction of the baseline fluctuation Higher slew rate


Better Time Resolution

Pulse shapes (137Cs) Baseline shapes

Details for T. Nishizawa, IEEE Trans. Nucl. Sci. 61 (2014) 1278

Two counter units aligned to bent electrons in BM4 Assuming identical timing

resolutions

Bias dependence: Bias tuning is important in the operation

Rate dependence Slight dependence… less significant than the bias dependence


Bias dependence

Rate dependence

Merit of the MPPC array Higher Quantum Efficiency at long wave length

region (𝜆 > 500 nm) than PMT Active area of 12.6 x 12.6 mm2

Sufficient number of pixels (57600 pixels) To be considered

Matching of emission and sensitivity spectra Linearity Decay time of MPPC signal & scintillation Dark count

Test Photosensors: Monolithic MPPC array (S11828-3344M(X1) ) Fine mesh PMT (H6152) for reference

Source: 137Cs (662 keV) Scintillators (by courtesy of T. Ishikawa @ ELPH): ½” NaI (Tl) (Housing with diffusing reflector) 16 x 16 x 16 mm3 BGO crystal (Teflon wrapped)


BGO

NaI (Tl)

Scintillators BGO NaI(Tl) LaBr3(Ce) Light yield (photons/MeV) *1 (8 – 10) x 103 38x 103 6.3 x 103

Temp. coef. of light yield (%/K) *1

-1.2 -0.3 0

Decay time (ns) *1 300 250 16

Density (g/cm3) *1 7.13 3.67 5.08

X0 (cm) 1.12*2 2.58*2 2.08

Estimated P. E. yield (photons/MeV)

MPPC (S10931-050)

PMT (H6152)

Size ½” 16 mm cube No sample

Measured Resolution [137Cs] (%(σ))

PMT (H6152)

Measured P. E. yield [137Cs] PMT (H6152)

Light Collection Eff. (%)

Expected P. E. yield [137Cs] MPPC


*1 Saint-Gobain Crystals, “Physical Properties of Inorganic Scintillators” *2 Particle Data Group

PMT Good matching

for NaI and LaBr3(Ce)

Long wave length tail of BGO is out of sensitive region

MPPC Good matching

for three scintillators

Integration to estimate the photo-electron yield


Fluctuation of single pulse fast response of PMT

Numerical integration was employed to obtain a histogram of a total output charge


NaI (Tl) BGO

Resolutions: 6.7 % for (NaI(Tl)) 2.2 x 102 photoelectrons 9.8 % for BGO 1.1 x 102 photoelectrons


NaI (Tl) BGO

Scintillators BGO NaI(Tl) LaBr3(Ce) Light yield (photons/MeV) *1 (8 – 10) x 103 38x 103 6.3 x 103

Temp. coef. of light yield (%/K) *1

-1.2 -0.3 0

Decay time (ns) *1 300 250 16

Density (g/cm3) *1 7.13 3.67 5.08

X0 (cm) 1.12*2 2.58*2 2.08

Estimated P. E. yield (photons/MeV)

MPPC (S10931-050)

4.1 x 103

17 x 103 24x103

PMT (H6152) 1.4 x 103 7.4 x 103 14 x 103

Size ½” 16 mm cube No sample

Measured Resolution [137Cs] (%(σ))

PMT (H6152) 9.8 6.7

Measured P. E. yield [137Cs] PMT (H6152) 1.1 x 102 2.2x102

Light Collection Eff. (%) 12 4.5

Expected P. E. yield [137Cs] MPPC (S10931-050)

3.2 x 102 5.1 x 102


*1 Saint-Gobain Crystals, “Physical Properties of Inorganic Scintillators” *2 Particle Data Group

Less than the number of pixels (57.6 x 103)

Numerical integration was employed Low pulse height comparable with a noise AC coupling significantly reduced the outpults


NaI(Tl) BGO

Photopeak associated pulse shape Broad base line dark counts?


NaI(Tl)

Amplitude spectra for baseline, baseline with dark counts and pulse associated with a scintillation of NaI(Tl) (Fast Fourier Transform (FFT))

A low pass filter (LPF) will reduce the dark counts


Frequency (Hz)

Am

plitu

de (V

)

Bandwidth limit by an LPF


0 0.8 1.6 2.4 3.2 4.0 Time (µs)

40

0

-40

-80 -120

-160

Vol

tage

(mV

)

Signal from the MPPC

Output of the amplifier

A Spice simulation for an LPF (cut off at 1.5 MHz) reduction of high frequency noise without significant effect on the true pulse Cooling of the system reduction of dark counts and increment of scintillation photons

Test with a real counter is underway

An MPPC based counter dedicated for the electron detector in the new photon tagger at ELPH 4 x 4 MPPC array of 3 x 3 mm2 effective area MPPC

elements Capacitance coupled amplifier for time resolution

and rate tolerance Good time resolution (< 50 ps(σ)) and sufficient rate

tolerance (up to 200 kHz) A counter with a crystal scintillator and the

MPPC array was studied Larger photoelectron yield than a PMT is expected Considerations on dark count rate and signal and

scintillation decay times are important


Department of Physics Tohoku University Hiroki Kanda

Documents

Transcript of Department of Physics Tohoku University Hiroki Kanda