Model 421 Series

PMT Base with  Preamplifier and HV Supply

The Model 421 Series photomultiplier (PMT) bases incorporating a preamplifier and a high voltage (HV) supply are intended for use with 10-stage PMTs fitted with standard 14-pin sockets. Each unit consists of a resistive divider/preamplifier and bias supply board.

For Models 421 and 421-3, a BNC receptacle (labeled SIGNAL) provides the pre-amplified signal output. The tail-pulse output is a positive-going pulse (Model 421) or negative-going pulse (Model 421-3). For Model 421-1, a BNC receptacle (labeled SIGNAL) provides either AC coupled anode output (negative) or pre-amplified output (positive). 

For all models, the output pulse has an approximately 50 μs tail for connection to a shaping amplifier. The output amplitude may be varied by HV bias adjustment.

Models 421 and 421-3 operate from a 12 Vdc supply only (NIM type 9-pin "D" connector). Model 421-1 operates on 8 - 18 Vdc power supplied either through the NIM compatible plug (9-pin "D") or through a 2.5 x 5.5 mm barrel plug.

• Specifications
• Documents

• Specifications
• Documents

Specifications

Model	421 & 421-3	421-1
Part Number	421: 47-3494 421-3: 47-3836	47-3720
Preamplifier	Gain fixed at approximately -2 V/V. Output of pre-amp is positive with a 500 ns rise time [NaI(Tl)] and approximately 50 µs "tail" pulse. Other decay times can be made available.	Gain fixed at approximately -3 V/V. Output of pre-amp is positive with a 500 ns rise time [NaI(Tl)] and approximately 50 µs "tail" pulse.
Output	BNC connector, approximately 50 ohms impedance. Maximum output amplitude is 10 V peak.	BNC connector, 50 ohms impedance. Maximum output amplitude is 10 V peak (with 12 V supply).
Rise Time	Less than 50 ns	Less than 50 ns
High Voltage	Adjustable between 0 and 1800 Vdc maximum	Adjustable between 0 and 1800 Vdc maximum
Dynode Divider Resistance	Total resistance is approximately 36 megohms, intended for low power and moderate to low count rate operation. Other variations can be made available.	Total resistance is approximately 43 megohms, intended for low power and moderate to low count rate operation. Other variations can be made available.
Power Consumption	Quiescent power is 250 mW at 12 Vdc	Quiescent power is 250 mW at 12 Vdc
NIM 9 pin "D"	Pin 1 & 2: GND Pin 3: VHV Pin 4: +12 Vdc Pin 8: GND to shut off HV	Pin 1 & 2: GND Pin 3: HV Read back (1000 V equals 1 V) Pin 4: +12 Vdc Pin 8: GND to shut off HV
Controls & Functions	SIGNAL: BNC connector providing pre-amplified signal output H Adj: Hole allowing access to the high-voltage bias adjustment screw H Test: A test point providing access to the PMT bias level (1000 V equals 1 V)	SIGNAL: BNC connector providing either anode (negative) output or pre-amplified signal (positive) output H Adj: Access to the high voltage bias adjustment screw H Test: A test point providing access to the PMT bias level (1000 V equals 1 V)
Size (Dia. x H)	5.8 x 10.7 cm (2.3 x 4.2 in.)	5.8 x 10.7 cm (2.3 x 4.2 in.)
Weight	0.16 kg (0.35 lb)	0.16 kg (0.35 lb)

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Documents

• Model 421 & 421-3 Product Manual
• Model 421-1 Product Manual

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