EG&G ORTEC 552 Panduan Pengoperasian dan Servis - Halaman 6

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ORTEC 552 PULSE-SHAPE ANALYZER AND TIMING SINGLE-CHANNEL ANALYZER

DESCRIPTION

1.1.

PURPOSE

The ORTEC 552 PSA/T-SCA provides a versatile group

of signal derivation functions. It can be used as either a

single-channel analyzer or as an integral discriminator;

by comparing the time relationships between its two sets

of outputs, information can be interpreted for pulse-

shape analysis. Each input signal that is accepted by the

adjusted amplitude criteria generates two separate

outputs, each precisely time-related to the input signal.

For reference in the instrument, one output signal is

generated through channel A and the other through

channel B.

The input logic circuits can be used in any of three modes,

selected by a front panel switch. The Integral mode uses

the adjusted lower-level discriminator as the only logic

reference and generates an output if the input signal

amplitude exceeds the lower level. The Normal mode

uses both lower-level and upper-level discriminators and

generates an output if the input amplitude exceeds the

lower-level bias but does not exceed the upper level; the

front panel Upper-Level control is adjusted within a range

of 0 to 10 V with ground as the zero reference point. The

Window mode operates the same as the Normal mode

except that the zero reference point for the Upper-Level

control is equal to the adjusted lower level and the range

of the Upper-Level control is 0 to 1 V. The lower level for

any mode can be furnished from the front panel control

or by a dc input signal through a rear panel connector.

An output signal through channel A is generated by the

constant-fraction method on the trailing edge of the input

signal, after the logic for acceptance has been completed.

The fraction is selectable at 10%, 20%, or 50% measured

down from the peak pulse height, using a jumper on the

printed circuit board to select the fraction. The output

occurs promptly at the constant-fraction point on the

trailing edge and is a NIM-standard fast negative output

pulse with excellent timing characteristics.

An output signal through channel B is also generated

by the constant-fraction method on the trailing edge of

the input signal. The fraction for channel B is selected by

a front panel switch that can be set for any level from 10%

through 100% (bipolar crossover) in 10% increments of

the peak pulse height. The unit must be strobed, either

internally or externally, for an output pulse to be provided.

When the rear panel switch selects internal strobe, the

channel B outputs are generated after an adjusted delay

following the constant-fraction trigger point; the delay

is adjusted on the front panel within the range of 0.1 to

1.1 /iS, permitting normalization for specific applications.

When the rear panel switch selects external strobe, the

channel B outputs are generated promptly when a NIM-

standard positive strobe is furnished through the rear

panel connector: the strobe signal must be furnished

within 10 MS after the channel B constant-fraction trigger

point. There are two channel B outputs; one is a NIM-

standard fast negative pulse and the other is a NIM-

standard slow positive pulse.

By using an internally-strobed channel B output, the

timing differentials between channels A and B can be

used to measure the decay characteristics of an input

pulse as the constant-fraction points of the two channels

are changed. For example, using a 50% fraction for

channel A and 10% for channel B, the time difference

on the decaying waveform can be measured by sub

tracting the channel B delay. In many applications, the

decay time of the pulse is significant for the type of par

ticle that is detected so the pulse shape can be used to

identify the nature of the source.

The 552 accepts either unipolar or bipolar input pulses

having either RC or delay-line pulse-shaped waveforms.

It includes an input attenuator so that an input amplitude

can be reduced by a factor of 1, 10, or 100, selected by

a front panel toggle switch. The walk of the attenuator

is typically less than 1 ns. This feature can be used to

optimize the timing accuracy of both output channels.

The walk characteristics can be optimized individually

in each channel, using a front panel screwdriver adjust

ment for each channel. When these controls are adjusted

properly, the walk characteristics for a bipolar delay-line

shaped input are less than 2.5 ns over a 200:1 dynamic

range of input amplitudes (see Fig. 1.1).

The instrument is designed to meet the interchangeability

standards recommended by USAEC Report TID-28093

(Rev). An ORTEC 401/402 Series Bin and Power Supply

provides all the necessary power through the rear panel

module connector. All signal levels and impedances are

compatible with other ORTEC NIM modules.

5 1,0

552 f = 0,5

Mi l

460 Amp Bipolar Output

Tektronix Attenuator

Channel 8

—

Channel A

1 1

40:1

60.1

80:1

100:1

200:1

Dynamic Range

Fig. 1.1. Typical Walk vs Dynamic Range.