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GASTOF Cherenkov with RF Phototube for FP420

Amur Margaryan

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Timing Workshop Krakow 2010

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Contents• Introduction

• RF time measuring technique

• Radio Frequency Phototube

• Optical Clock

• H3 Single Photon Timing Technique

• GASTOF Cherenkov with RF phototube

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Introduction Regular timing technique in high energy and nuclear physics experiments:1) Time information is transferred by secondary electrons - SE or photoelectrons -

PE;2) The SE and PE are accelerated, multiplied and converted into electrical signals,

e.g. by using PMTs or other detectors;3) Electrical signals are processed by common nanosecond electronics like

amplifiers, discriminators and time to digital converters, and digitized.

Figure: schematic layout of the regular timing techniquea) Nanosecond signal processing; Rate ~ few MHzb) The time measurement error of single PE or SE is in range 50-100 ps (FWHM).c) The time drift is ~1ps/s (mainly due to electronics).

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1) Time information is transferred by SEs or PEs;2) The electrons are accelerated and deflected by means of ultra high frequency RF fields;

Parameters:

a) The limit of precision of time measurement of single SE or PE is σ ≈ 1 ps;b) High and long-term stability - 200 fs/h - can be reached;c) Time drift is ~10fs/s;d) Image processing; rate is ~10 kHz.

Radio Frequency Time Measuring Technique or Streak Camera Principle or Oscilloscopic Method

Figure: Schematic of the radio frequency time measuring technique

Image Readout, e.g. by using the

CCD

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Radio Frequency PhototubeOperates like circular scan streak camera but provides nanosecond

signals like regular pmt

CW SE beam

Single SE

Parameters:a) Timing dispersion is similar to streak cameras b) Provides nanosecond signals like regular PMT; rate ≈ few MHz

A. Margaryan et al., Nucl. Instr. and Meth. A566, 321,2006

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Position Sensitive Anodes

Resistive Anode Multi Pixel Anode

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RF phototube with point-like photocathode

The schematic layout of the RF phototube with point-like photocathode. 1 - photo cathode, 2 - electron-transparent electrode, 3 - electrostatic lens, 4 - RF deflection electrodes, 5 - image of PEs, 6 - λ/4 RF coaxial cavity, 7 - SE detector.

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RF phototube with large-size photocathode

The schematic layout of the RF phototube with large-size photocathode. 1 - photo cathode (for 4 cm diameter photocathode the time dispersion of PE is

≤10 ps, FWHM), 2 - electron-transparent electrode, 3 - transmission dynode, 4 - accelerating electrode, 5 - electrostatic lens, 6 - RF deflection electrodes, 7 - image of PEs, 8 - λ/4 RF coaxial cavity, 9 - SE detector.

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Uncertainty sources of time measurement with f = 500 MHz RF field

1. Time dispersion of PE emission ≤ 1 ps

2. Time dispersion of electron tube: chromatic aberration and transit time ≤ 2 ps

3. So called “Technical Time Resolution” of the deflector: σ = d/v, where d is the size of the electron spot, v = 2πR/T is the scanning speed. For our case d = 1 mm, R = 2 cm, T = 2 ns ~20

ps

TOTAL ~21 ps

THEORETICAL LIMIT OF THE TECHNIQUE ~1 ps

1010

])(2sin[)( 000RFRFRFRFRF ttVtV RF signal 0

RFV - is constant

0RF - nominal frequency

)(tRF

0RF - nominal phase

- deviations: random and systematic

TRF

iT

iRF

iRF

iRF ttt ,00 )()(2

TRF

iT

iRF

iRF

iRF ttt ,011101 )()(2

TRFii

RFiRF

iRFRF tt )(2 101

RF timing: stand-alone operation, random photon source

)()( 1 iRF

iRFRF tt

)()( 1 iT

iTT tt

)(tTand

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Stand-alone operation: periodic photon source

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])(2sin[)( 000RFRFRFRFRF ttVtV

)()()(2)( 000 tttt TRFHphRFH

)(2 00phRFR

00phRF 00phRF

00phRF

drift speed on the scanning circle

drift is clockwise

drift is counterclockwise

Synchroscan mode

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RF timing: synchroscan operational mode

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Ideal RF synthesizer and tube

0)()()( REFTRFREF ttt

0)()( tt TRF

Position of photoelectrons stay stable on the scanning circle

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Time drift: synchroscan mode

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Time drift of the streak cameras < 10 fs/sW. Uhring et al., Rev. Sci. Instr. V.74, 2003

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Synchroscan mode: experiment with reference beam

00 )()(2 REFREF

TREF

RFREF

phREFRF ttt

00 )()(2 EXPEXP

TEXP

RFEXP

phEXPRF ttt

TRFREFEXP

RFREFRF

EXPRF tt )(2 0

)()( REFRF

EXPRFRF tt

)()( REFT

EXPTT tt

Random and Systematic time drifts due

to RF Synthesizer and RF Phototube

Schematic of the setup

For stt REFEXP 1 they can be ignored and stability will be determined by statistics only

For single PE psd 20 for sN /1061 fsNd 20/ 1

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Drift of relative measurements

A. Margaryan Yerevan,19 May 2010 15

Long-term stability (~200 fs) of streak cameras with reference photon beam W. Uhring et al., Rev. Sci. Instr. V.74, 2003

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To drive RF phototube

RF Phototube and Optical Clock

013 n

Optical Clock or Femtosecond Optical Frequency Comb Technique Transformed Coherently Optical Frequencies into the Microwave Range

Schematic of the optical clockwork, J. L. Hall, Nobel lecture, 2005

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Femtosecond Optical Frequency Comb as a multipurpose frequency synthesizer

,

Depicted from T. M. Ramond et al., 2003

Fractional instability of optical clocks 10-18

Fractional instability of rf synthesizer < 10-20

/20 fs /fs

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RF phototube + optical clock = 3H timing technique for single photons

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Schematic layout of the synchroscan mode of RF phototube with optical clock.

Optical Clock is used as a source of RF frequencies to operate the RF phototube and as a reference photon beam to minimize or exclude the time drifts due to RF synthesizer

and phototube.

Time precision determined by single photon time resolution and statistics !!!

A. Margaryan, article in press, doi: 10.1016/j. nima, 2010.08.122

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Conclusions

Radio Frequency Phototube + Periodic Photon Source (Accelerator, Optical Clock etc)

= H3 Single Photon Timing Technique

• High resolution, 20 ps for single PE (limit ~ ps)

• High rate, few MHz

• Highly stable, 10 fs/day

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ApplicationsNuclear Physics:

• Absolute calibration of the magnetic spectrometers; Precise mass measurements; delayed pion spectroscopy of hypernuclei; precise lifetime measurements

Fundamental Tests:

• Gravitational Red-Shift Measurement; Light speed anisotropy

Biomedical applications

• Diffuse optic imaging; Fluorescence lifetime imaging; TOF-PET

Other applications

• Quantum cryptography

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Cherenkov Time-of-Flight (TOF) and Time-of-

Propagation (TOP) Detectors Based on RF Phototube

The time scale of Cherenkov radiation is ≤ 1ps, ideal for TOF

The schematic of Cherenkov TOF detector in a “head-on” geometry based on RF phototube

RF Cherenkov picosecond timing technique for high energy physics applications,

A. Margaryan, O. Hashimoto, S. Majewski, L. Tang, NIM, A595, 2008, 274

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Time distribution of p = 5000 MeV/c pions in “head-on”

CherenkovTOF detector with L = 1 cm quartz radiator.

a) Time distribution of single photoelectrons

b) Mean time distribution of 150 photoelectrons

c) Mean time distribution of 100 photoelectrons

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Fast Timing for FP4202cm

331053310)107(

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Luminosity1s Timing Resolution ps

33102 10

5

Event rate at maximum luminosity is ~ 10 MHz

Few events in a 1ns time interval is needed to be detected

Time stability ~ 1ps

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GASTOF Cherenkov

Schematic of the GASTOF Cherenkov ant its intrinsic time resolution.

Depicted from the FP420 R&D Project

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GASTOF Cherenkov with RF phototube

Schematic of the GASTOF Cherenkov with RF phototube

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Readout Electronics

Schematic of the Readout Scheme with Multi Pixel Anode

The expected at maximum luminosity 10 MHz rate the RF deflector is distributed among ~100 pixels. Each pixel will operate as an independent PMT with ~0.1 MHz rate.

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Conclusion

GASTOF with Radio Frequency Phototube

Intrinsic Time resolution few ps

Rate 10 MHz

Stability < 1 ps/hrs

Ability to detect several ten events in a ns period

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THANK YOU