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計測機器 EG&G ORTEC 463のPDF 操作・サービスマニュアルをオンラインで閲覧またはダウンロードできます。EG&G ORTEC 463 20 ページ。 Constant fraction discriminator

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7. APPLICATIONS

7.1. TIMING WITH FAST SCINTILLATORS

7.2. TIMING WITH LARGE Ge(Li) DETECTORS

Figure 7.1 shows a typical system for timing with fast

scintillation detectors such as Nation-136, Pilot B, NE-102,

NE-111, NE-213, etc. The 463 Constant Fraction Dis

criminator is used in the stop channel of the time to pulse

height converter. Figures 7.2 and 7.3 are typical timing

spectra that were taken with this system. The spectrum

of Fig. 7.2 was taken with a narrow dynamic range (20:1)

of pulse heights on both start and stop channels, and the

spectrum of Fig. 7.3 was taken with a wide dynamic

range (100:1). See the Bibliography at the end of this

section for a l ist of more detailed discussions on timing

with fast scintil lators.

The input to the 463 should have approximately 10-V

pulses for the Compton edge of the 51 TkeV gamma

in order to obtain a 100:1 dynamic range. The lower

level discriminator should be set at 'V50 mV. For some

tubes the 50^2 back termination internal to the tube base

must be removed to accomplish the maximum dynamic

range.

Figure 7.4 is a block diagram of another gamma-gamma

coincidence system. In this system the start channel uses

a fast scintillator and the stop channel employs a large

coaxial Ge(Li) detector. A typical plot of the time

resolution as a function of energy is shown in Fig. 7.5

for a large Ge(Li) detector, and a typical timing spectrum

for a wide dynamic range is shown in Fig. 7.6.

To obtain the maximum dynamic range, the maximum

pulse height of interest should correspond to 'ViO V at

the output of the ORTEC 454 Timing Filter Amplifier.

Slight saturation wil l not distort the timing spectrum if

the 10% to 90% rise time for the saturation pulses

is greater than 20 nsec. The Int (Integrate) time constant

should be no greater than 5 or 10 nsec and the Diff

(Differentiate) time constant should be >100 nsec on the

454 Amplifier.

If an early peak appears in the time spectrum, it usually

means that the Level Discriminator is set slightly too

low on the 463 and that it is enabled falsely.

ORTEC

456

HV POWER

SUPPLY

ORTEC

403A

TIME

PICKOFF

CONTROL

270

RCA

8575

PM BASE

a Source

ORTEC

265

RCA

8575

PM BASE

l-x 1-in. NATON-136

ORTEC

457

TIME TO

PULSE HEIGHT

CONVERTER

ORTEC

451

ORTEC

455

ORTEC

418A

SPECTROS-

CONST

COPY

FRACTION

COINCIDENCE

AMPLIFIER

TIMING SCA

Stop

ORTEC

425

NANOSECOND

DELAY

ORTEC

455

CONST

FRACTION

TIMING SCA

ORTEC

451

SPECTROS-

COPY

AMPLIFIER

MULTICHANNEL

ANALYZER

ORTEC

456

HV POWER

SUPPLY

Dynode

ORTEC

463

CONST

FRACTION

DISCRIMIN

ATOR

ORTEC

113

SCINTILLA

TION

PREAMP

Fig. 7.1. A System for Gamma-Gamma Lifetime Measurement.