Transcript Margaryan_GASTOF_2010_11.29

GASTOF Cherenkov with RF Phototube for FP420
Amur Margaryan
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 technique
a) Nanosecond signal processing; Rate ~ few MHz
b) 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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Radio Frequency Time Measuring Technique
or Streak Camera Principle or Oscilloscopic Method
1) Time information is transferred by SEs or PEs;
2) The electrons are accelerated and deflected by means of ultra high frequency RF fields;
Image
Readout, e.g.
by using the
CCD
Figure: Schematic of the radio frequency time measuring technique
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.
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Radio Frequency Phototube
Operates like circular scan streak camera but provides nanosecond
signals like regular pmt
CW SE beam
Parameters:
a) Timing dispersion is similar to streak cameras
b) Provides nanosecond signals like regular PMT; rate ≈ few MHz
Single SE
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
THEORETICAL LIMIT OF THE TECHNIQUE
~21 ps
~1 ps
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RF timing: stand-alone operation, random photon source
RF signal
0
0
0
VRF (t )  VRF
sin[ 2 RF
t   RF (t )   RF
]
0
- is constant
V RF
0 - nominal frequency
 RF
0
 RF
0 i
0,T
 iRF  2 RF
t  RF (t i )  T (t i )  RF
1
0 i 1
0,T
iRF
 2 RF
t  RF (t i 1 )  T (t i 1 )  RF
 RF  
i 1
RF

i
RF
 2 (t
0
RF
i 1
 t )  RF  T
i
- nominal phase
 RF   RF (t i 1 )   RF (t i )
T  T (t i 1 )  T (t i )
 RF (t ) and T (t ) - deviations: random and systematic
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Stand-alone operation: periodic photon source
0
0
0
VRF (t )  VRF
sin[ 2 RF
t   RF (t )   RF
]
0
 H (t )  2 ( RF
 0ph )t  H0  RF (t )  T (t )
0
  2R( RF
 0ph )
drift speed on the scanning circle
0
 RF
  0ph
drift is clockwise
0
 RF
  0ph
drift is counterclockwise
0
 RF
  0ph
Synchroscan mode
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RF timing: synchroscan operational mode
0
 REF (t )  RF (t )  T (t )  REF
Ideal RF synthesizer and tube
RF (t )  T (t )  0
Position of photoelectrons stay stable on the scanning circle
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Time drift: synchroscan mode
Time drift of the streak cameras < 10 fs/s
W. Uhring et al., Rev. Sci. Instr. V.74, 2003
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Synchroscan mode: experiment with reference beam

REF
RF
 2 t
0 REF
ph
 RF (t
REF
)  T (t
REF
) 
0
REF
Schematic of the setup
0 EXP
EXP
EXP
0
 EXP

2

t


(
t
)


(
t
)


RF
ph
RF
T
EXP
REF
0
EXP
 EXP
 t REF )  RF  T
RF   RF  2 RF (t
 RF   RF (t EXP )   RF (t REF )
T  T (t EXP )  T (t REF )
For
Random and Systematic time drifts due
to RF Synthesizer and RF Phototube
t EXP  t REF  1s they can be ignored and stability will be determined by statistics only
For single PE
 d  20 ps
for
N1  106 / s
 d / N1  20 fs
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Drift of relative measurements
Long-term stability (~200 fs) of streak cameras with reference photon beam
W. Uhring et al., Rev. Sci. Instr. V.74, 2003
A. Margaryan
Yerevan,19 May 2010
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RF Phototube and Optical Clock
Optical Clock or Femtosecond Optical Frequency Comb Technique
Transformed Coherently Optical Frequencies into the Microwave Range
3  n  1  0
To drive
RF phototube
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 < 20 fs / 
10-20
 fs / 
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RF phototube + optical clock = 3H timing technique for single photons
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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Applications
Nuclear 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-ofPropagation (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 FP420
2 1
cm
s
Luminosity
210
33
5 10
33
(7  10) 10
Timing Resolution ps
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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
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