EG&G ORTEC 414A Betriebs- und Wartungshandbuch - Seite 6

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ORTEC 414A FAST COINCIDENCE

1. DESCRIPTION

The

414A

Fast

Coincidence

allows fast coincidence

determination between any two or three input signals. A

dc-coupled anticoincidence input is provided to inhibit the

coincidence

output. The coincidence

output can be

inhibited by a dc voltage or a pulse that overlaps the period

of coincidence of the coincident pulses. The resolving time

of the anticoincidence circuit is set by the width of the

input pulse. The resolving time (2t) of the Fast Coincidence

unit may be varied over a 10- to 110-nsec range by a

10-turn control for accurate resettability of the resolving

time. All four inputs are controlled by In/Out toggle

switches. Input signal requirements are compatible with

NIM slow positive logic output signals of a variety of

ORTEC timing equipment. The output pulse is suitable as

an input to the 418A Universal Coincidence module and

other modules of the ORTEC 400 Series requiring a logic

input pulse. The module obtains the necessary operating

power from an ORTEC 401/402 Series Bin and Power

Supply. The output signal and all signal inputs use front

panel BNC connectors.

The instrument is designed to meet the recommended

interchangeability standards outlined in USAEC Report

TID-20893 (Rev). An ORTEC 401/402 Bin and Power

Supply provides all necessary power through the rear

module connector. All signal levels and impedances are

compatible with other modules in the ORTEC 400 Series.

The 414A is basically a threefold AND circuit, with each

input to the AND circuit regenerated, or reshaped, to a

standardized waveform in passing from the input connector

to the actual AND circuit. The general connotation of the

word "fast" tends to be in terms of elapsed time or speed,

but in this instrument the term "fast" is actually intended

to indicate the general nature of the coincidence circuit;

i.e., the

input pulses are

reshaped

and

the actual

coincidence determination is made on the leading edge, or

leading portion, of the input pulses.

The three coincidence inputs to the 414A- feed into

identical but separate shaper circuits. The shaper circuit

contains a voltage limiter to allow a wide dynamic range of

input pulse amplitudes. The output of the limiter feeds into

a regeneration circuit, where a standard pulse is generated

for each input pulse regardless of the actual waveform of

the input signal. This standard pulse is then fed into the

resolving time network, where it is reshaped to satisfy the

2r resolving time selected via the front panel Resolving

Time control. The outputs of the three resolving time

networks are fed in parallel to an "overlap" coincidence

network, i.e., an AND network. When portions of the

reshaped input pulses overlap each other, the AND circuit

recognizes a coincidence event within the resolving time set

on the front panel Resolving Time control and produces an

output. The coincidence recognition output from the AND

circuit

may

inhibited

signal

from

the

anticoincidence input. This inhibit signal may be a pulse or

a dc voltage since the anticoincidence circuit is dc-coupled.

The inhibit period is determined by the width of the input

pulse. If the output from the AND circuit is not blocked by

the anticoincidence circuit, it is regenerated into a standard

output signal from the 414A, indicating that a coincidence

event has been detected.

The coincidence inputs are controlled by front panel toggle

switches, which permit selection of one-, two-, or threefold

coincidence.

switch

also

provided

for

the

anticoincidence input. These switches allow each input to

be disabled without the associated coaxial cable having to

be removed.

2. SPECIFICATIONS

2.1. PERFORMANCE

2.2. CONTROLS

Pulse Pair Resolution

<100 nsec on any single input; for

coincidence events, <1 psec on the coincidence output.

Resolving Time (2r) Continuously variable from 10 to 110

nsec for coincidence signals; set by the width of the input

pulse for the anticoincidence signal.

Temperature Instability 2t changes <0.2%/°C, 0 to 50°C.

Resolving Time, 10-110 nsec Front panel 10-turn poten

tiometer for controlling resolving time for inputs A, B, and

C over a range of 10 to 110 nsec.

In/Out Toggle switches for using any input combination

desired and for disabling input signals to the coincidence

and anticoincidence circuits without input coaxial cables

having to be removed.