EG&G ORTEC 463 Operating And Service Manual - Page 17

Browse online or download pdf Operating And Service Manual for Measuring Instruments EG&G ORTEC 463. EG&G ORTEC 463 20 pages. Constant fraction discriminator

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11
ORTEC
456
HV POWER
SUPPLY
2- by 2 in. Naton 136
RCA
8575
/
ORTEC
124
265
/
*
Ge(Li)
PM BASE
PM TUBE
6-mm
PREAMP
^ * Na Source
ORTEC
463
CONST
FRACTION
DISCRIMI
NATOR
ORTEC
457
Stop
ORTEC
425
TIME TO
PULSE HEIGHT
CONVERTER
NANOSECOND
DELAY
i
ORTEC
442
ORTEC
416A
LINEAR GATE
AND
STRETCHER
GATE
AND DELAY
GENERATOR
ORTEC
463
CONST
FRACTION
DISCRIMI
NATOR
ORTEC
455
CONST
FRACTION
TIMING SCA
ORTEC
454
TIMING
FILTER
AMPLIFIER
ORTEC
451
SPECTROS-
COPY
AMPLIFIER
ORTEC
456
HV POWER
SUPPLY
MULTI
CHANNEL
ANALYZER
Fig. 7.10. Fast Coincidence System Using a Gel Li) 6-mm Low Energy Photon Spectrometer.
80
120
Energy (keV)
Fig. 7.11. Time Resolution vs Energy for a 6-mm Low
Energy Photon Spectrometer.
451 and 455, the Compton scattering can produce a
timing spectrum at the desired energy.
The system with the block diagram in Fig. 7.10 can also
be used for a l ifetime measurement of an excited state.
A typical example is seen in the decay from the 136-keV
state of '''Co. The decay from the 136-keV state to the
ground state is by way of 122 keV to a 14-keV state,
and the electron has an approximate 100-nsec lifetime
in the 14-keV state. Thus the start channel can be activated
by the 122-keV gamma ray, and the slow channel of
the stop side can be adjusted to observe only the 14-keV
gamma ray: the l ifetime of the 14-keV state can then be
measured and recorded. A spectrum showing typical
results of this measurement is shown in Fig. 7.12.
7.5. TIMING WITH Nal(TI) SCINTILLATORS
This type of measurement is similar to timing with fast
scintillators except for one additional problem that must
be considered. The photoelectron statistics are so poor for
low-energy gamma-ray work that individual photoelectron
events near the trail ing edge of the Nal(TI) pulses will
trigger the 463. Thus a single scintillation event can
10,000
7,000
4,000
Z 1,000
o
700
280 psec/Channel
200
600
800
Channel Number
1,000
1,200
1,400
Fig. 7.12. Spectrum of the Lifetime of the 14-keV State
in the Decay of " Co.