A1421
New
Preamplifier and Discriminator for 3He tubes
Features
- Specifically designed for neutron detectors as 3He or BF3 tubes in counting applications
- Gain: 30 mV/fc on HiZ (15 mV/fC on 50 Ω)
- Discriminator with adjustable threshold
- Analog and Logic discriminator output
- Compact size
- External HV input on SHV connector (feeding the internal decoupling circuits)
- Detector input on SHV or HN connectors
- Input bias voltage: ± 4 kV Max
- Test input on LEMO (1 pF charge injection capacitors)
- Full counting acquisition system in combination with R7771B Neutron Pulse Train Recorder or R7780 Shift Register
Overview
The CAEN Mod.A1421 is a charge-sensitive preamplifier, shaper, and discriminator that provides both analog and logic outputs. It is designed for use with neutron detector tubes in various applications. The preamplifier is optimized for position-sensitive thermal neutron detectors, where high counting rates and good spatial resolution (low noise) are required. It is also suitable for counting applications when used with monitor counters like the R7771B and R7780, such as in the non-destructive analysis of nuclear materials by passive or active neutron methods for containment monitoring and waste control.
The device is equipped with a detector input on an SHV or HN connector and an external HV input on an SHV connector (which powers the internal decoupling circuits). Additionally, it features two rear 3-pin male connectors (ref.: RT3MP REAN) to power the preamplifier, also allowing for daisy-chain operation. It includes two trimmers to adjust the discriminator threshold and the discriminator output width. A digital input is available on a LEMO connector for cascading the summing of the discriminator signals.
The preamplifier can be powered directly by the R7771B or by the A325 DC/DC power supply unit. Compatible power cables, models A324 (1 meter) and A323 (20 centimeters), are available as accessories. The A1421 is supplied with the A324 cable to ensure seamless integration with the power supply and detector setup.
Two versions of this preamplifier have been designed: a standard version (Version A), suitable for most applications, and a version for active measurements (Version B), where the sample is activated using a neutron generator. Version A includes a polezero compensation circuit and is suitable for applications requiring Pulse Height Analysis (PHA), where neutron spectroscopy or position sensitivity may be needed alongside neutron counting. In contrast, Version B provides bipolar output pulses that are not pole-zero compensated and includes dedicated optimizations required for active interrogation measurements, ensuring a fast recovery from saturation conditions once the neutron generation burst is complete.
Developed in collaboration with Institut Laue-Langevin in Grenoble.
Technical Specifications
- GENERAL
- Form Factor: Enclosure Aluminum box. Size:
- 94 W x 157.5 L x 38 L mm³ (including BNC connectors)
- 94 W x 155.5 L x 38 L mm³ (including HN connectors)
- 94 W x 119.5 L x 38 H mm³ (without connectors)
- Weight 350 g.
- Form Factor: Enclosure Aluminum box. Size:
- POWER CONSUMPTION
Input Voltage: ± 12 V
+12 V 65 mA (Typ)
-12 V 45 mA (Typ)
Two rear 3-pin male connectors for power daisy chain
- DETECTOR INPUT
- Input connector: BNC or HN
- AC coupled
- Positive or negative input polarity accepted
- Input charge range: ± 90 fC
- ESD protected input
- HV IN (Detector Bias)
- Bias connector: BNC
- Operating voltage: max ± 4 kV
- TEST
- LEMO connector
- Injection capacitance: 1 pF
- 10:1 Attenuation
- 50 Ω Impedance
- Preamplifier and Shaper (A OUT)
- Non inverting
- Output impedance: 50 Ω
- Gain: 30 mV/fc on HiZ (15 mV/fC on 50 Ω)
- Shaping:
- Rise time: 120ns
- Fall time: 460 ns
- FWHM: 350 ns
- Time to baseline (5% of the maximum amplitude: 750 ns (A1421A), 2000 ns (A1421)
- Output range: ± 2.6 Vpp on HiZ (± 1.3 Vpp on 50 Ω)
- Recovery time after saturation:
- A1421A: 2 ms
- A1421B: 60 us
- Noise 2 mV RMS on 50 Ω (on the baseline, with open input)
- Resolution 0.32 fC @ Qin = 80 fC (=0.4%)
- Output on LEMO connector
- DISCRIMINATOR (D OUT/D IN)
- Variable threshold, adjustable from –1V to +1 V via front panel 12 turn trimmer
- Minimum threshold: 20 mV (min. threshold above the noise)
- Minimum detectable signal (min 99% signal detected): 13 mV (0.86 fC)
- Threshold voltage monitor output on testpoint
- TTL output on LEMO Connector
- Programmable output width between 35 to 600 ns via front panel 12 turn trimmer
- Can drive 50 Ω
- TTL In on LEMO connector (Zin = 1 kΩ) for cascade summing
- LED for signal activity (green when inactive, RED when active)
- Pulse pair resolution (minimum separation between pulses): 800 ns
- ENVIRONMENTAL
- Indoor use
- Operating Humidity: 10% ± 90% RH non condensing
- Storage Humidity: 5% ± 90% RH non condensing
- Pollution Degree: 2
- Altitude: <2000 m
- Overvoltage Category: II
- EMC Environmental Commercial
- Operating Temperature range: 0°C +50°C
- Storage Temperature range: -10°C +80°C
Ordering Options
| Code | Description |
|---|---|
| WA1421BHXAAA | A1421BH - Preamp. and discriminator for He3 Tubes for active measurements (HN Det. In Conn.) RoHS |
| WA1421AHXAAA | A1421AH - Preamp. and discriminator for He3 Tubes for passive measurements (HN Det. In Conn.) RoHS |
| WA1421ASXAAA | A1421AS - Preamp. and discriminator for He3 Tubes for passive measurements (SHV Det. In Conn.) RoHS |
| WA1421BSXAAA | A1421BS - Preamp. and discriminator for He3 Tubes for active measurements (SHV Det. In Conn.) RoHS |