NIM Model 375L 8-Fold Coincidence Unit

WITH VETO

The LRS Model 375 8-Fold Coincidence Unit accepts standard NIM logic signals at eight independent logic inputs and a separate fast veto input. It permits direct detection of simultaneity among up to eight signals, an operation that formerly required a cascade of lower order coincidences. This achieves a significant reduction in module count and logic delay. Front panel programming pins permit any of the logic inputs to be selectively disabled to permit lower order coincidences. The veto input inhibits the unit regardless of the state of the logic inputs. Once triggered by signals satisfying the input coincidence requirements, the 375L generates six NIM fast logic outputs: two dual (-32 mA) negative outputs and one dual complementary output. A single output pulse is produced regardless of input amplitude or duration (no-multiple-pulsing). The output pulse duration of the 375L may be continuously preset from 4 ns to 50 ns from the front panel by means of a multiturn potentiometer. The duration is independent of input overlap time, amplitude, and rate. Because it is updating, it may be retriggered even before the end of an output pulse that is already present.

The Model 375L is a modern MECL Ill integrated circuit design which respects normal NIM power dissipation standards and does not require special power bins or voltages.

NIM Model 375L 8-FOLD COINCIDENCE UNIT with veto

Specifications

INPUT CHARACTERISTICS

Logic Inputs:

Eight; direct-coupled; impedance 50 OHm; -600 mV threshold maximum; reflections < 10% for inputs of 2 ns risetime; each input has separate disable selector. Any input serves as inhibit when driven with comple- mentary signal.

Slow (Bin) Gate:

Via rear connector, with rear panel On-Off switch; rise and fall times approximately 20 ns, quiescently above + 4 volts, clamping to ground inhibits; direct-coupled.

Veto:

Separate master veto input; direct-coupled; rise and fall < 2 ns; need only overlap the earliest time of input coincidence.

OUTPUT CHARACTERISTICS

Outputs:

Three; one positive (quiescently - 32 +/-l mA, 0 mA during output), two negative (0 mA quiescently, -32 +/-l mA during output); pulse width equal to preset output duration. Updating.

Fan-Out:

Maximum of 6-fold, if each output drives two terminated 50 Ohm inputs.

Duration:

Continuously adjustable 4.0 to 50 ns; front panel screwdriver-adjustable potentiometer; jitter on shortest range less than 20 ps rms.

Rise and Fall Time:

Risetime: 1.2 ns typical; falltime slightly longer except at minimum width.

GENERAL

Maximum Rate:

150 MHz minimum, input and output.

Double-Pulse Resolution:

Typical 5 ns; (6.5 ns for triple pulses).

Coincidence Width:

Determined by input pulse durations; total widths in realistic system approximately 1 ns up without limit. Ideally, the FWHM of narrowest coincidence curve (see "Time Resolution" below).

Time Resolution:

Counting rate down by a factor of 100 in 15 ps at either edge of coincidence curve, when two inputs are driven from two outputs of a Model 321 B discriminator; in 60 ps when driven from separate discrimina- tors triggered by a single Model IP-1 Instapulser.

Coincidence Overlap:

4 ns typical (3 ns for coincidence levels <3).

Counting Efficiency:

Recovery time typically less than output pulse duration; no deadtime following output pulse at output durations greater than approximately 6 ns.

Input-Output Delay:

Absolute delay: 8 ns; jitter < 20 ps rms.

Multiple-Pulsing:

None; one and only one output pulse of preset duration is produced each time the input conditions are satisfied, regardless of the duration of the input pulses or,their overlap.

Packaging:

In conformance with AEC standard for nuclear modules (AEC Report TID-20893); RF shielded AEC #1 module, fitting 12 per bin; dimensions 1.35 x 8.75 x 10 inches deep. Completely compatible physically and electrically with LRS Power Chassis Model 108P, and with any other AEC power bin of any manufacturer; Lemo connectors.

Power Requirements:

+ 12 VDC at < 30 mA;
- 12 VDC at 100 mA;
120 VAC at 33 mA.

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INPUT CHARACTERISTICS
Logic Inputs:	Eight; direct-coupled; impedance 50 OHm; -600 mV threshold maximum; reflections < 10% for inputs of 2 ns risetime; each input has separate disable selector. Any input serves as inhibit when driven with comple- mentary signal.
Slow (Bin) Gate:	Via rear connector, with rear panel On-Off switch; rise and fall times approximately 20 ns, quiescently above + 4 volts, clamping to ground inhibits; direct-coupled.
Veto:	Separate master veto input; direct-coupled; rise and fall < 2 ns; need only overlap the earliest time of input coincidence.
OUTPUT CHARACTERISTICS
Outputs:	Three; one positive (quiescently - 32 +/-l mA, 0 mA during output), two negative (0 mA quiescently, -32 +/-l mA during output); pulse width equal to preset output duration. Updating.
Fan-Out:	Maximum of 6-fold, if each output drives two terminated 50 Ohm inputs.
Duration:	Continuously adjustable 4.0 to 50 ns; front panel screwdriver-adjustable potentiometer; jitter on shortest range less than 20 ps rms.
Rise and Fall Time:	Risetime: 1.2 ns typical; falltime slightly longer except at minimum width.
GENERAL
Maximum Rate:	150 MHz minimum, input and output.
Double-Pulse Resolution:	Typical 5 ns; (6.5 ns for triple pulses).
Coincidence Width:	Determined by input pulse durations; total widths in realistic system approximately 1 ns up without limit. Ideally, the FWHM of narrowest coincidence curve (see "Time Resolution" below).
Time Resolution:	Counting rate down by a factor of 100 in 15 ps at either edge of coincidence curve, when two inputs are driven from two outputs of a Model 321 B discriminator; in 60 ps when driven from separate discrimina- tors triggered by a single Model IP-1 Instapulser.
Coincidence Overlap:	4 ns typical (3 ns for coincidence levels <3).
Counting Efficiency:	Recovery time typically less than output pulse duration; no deadtime following output pulse at output durations greater than approximately 6 ns.
Input-Output Delay:	Absolute delay: 8 ns; jitter < 20 ps rms.
Multiple-Pulsing:	None; one and only one output pulse of preset duration is produced each time the input conditions are satisfied, regardless of the duration of the input pulses or,their overlap.
Packaging:	In conformance with AEC standard for nuclear modules (AEC Report TID-20893); RF shielded AEC #1 module, fitting 12 per bin; dimensions 1.35 x 8.75 x 10 inches deep. Completely compatible physically and electrically with LRS Power Chassis Model 108P, and with any other AEC power bin of any manufacturer; Lemo connectors.
Power Requirements:	+ 12 VDC at < 30 mA; - 12 VDC at 100 mA; 120 VAC at 33 mA.