USB-MCA: 8K Multi-Channel Analyzer with
PHA and MCS Modes and USB Interface

USB-MCA unit

Introduction 

A Multi-Channel Analyzer (MCA) is major part of a nuclear spectroscopy system. To meet the requirements of a range of applications, an MCA with Universal Serial Bus interface (USB-MCA) has been developed by Electronics Division BARC. It supports the PHA (Pulse Height Analysis) as well as the MCS (Multi-Channel Scaling) operational modes. The support for the MCS mode has been newly implemented in the USB-MCA without altering its original PHA functionality.

In the PHA mode, the resolution of the USB-MCA ranges from 256 channels to 8K channels, making it suitable for a wide range of energy spectroscopy applications from low resolution (e.g. NaI-PMT) to high resolution (e.g. HP-Ge) systems. In the MCS mode, the USB-MCA can be used for Mössbauer spectroscopy.

The new PHAST-MCS application software provided with the USB-MCA, seamlessly integrates with the hardware, featuring a range of standard functions.

The USB-MCA, along with an external detector, spectroscopy amplifier and HV supply, can be used for various energy spectroscopy applications. Also, with appropriate detector, amplifier and Mössbauer drive unit, it can be used for Mössbauer spectroscopy.

Specifications

General
 

Analog input type	: Positive, unipolar, shaped pulses from external amplifier
Analog input range	: 0 to +10 volts, with minimum 1 µs shaping time constant
Preset Acquisition Time	: Live or Clock, 1 to 99,99,99,999 seconds
Max counts / channel	: 31 bit (2 billion)
LLD, ULD, Baseline	: Digitally set through application software
Power requirement	: 5V, ~ 500 mA through USB bus cable
Dimensions	: 220(L) x 85(W) x 35(H)mm

PHA Mode
 

MCA resolution	: 256, 512, 1K, 2K, 4K and 8K channels
Pulse processing time	: 7 µs including ADC conversion time
Pile up rejection (PUR)	: TTL input from spectroscopy amplifier
DNL	: + 1 %
INL	: +  0.05 % full scale

MCS Mode
 

Dwell time setting	: 10 µs to 999 seconds internal dwell timer
Time-base output	: 1µs active-high LVTTL pulse output driven by internal (on board) dwell timer
Sync pulse input	: 1µs active-high LVTTL input from external hardware
Pass length	: 1024 channels
Acquisition mode setting	: Add or Overwrite previous count

Advantages

The USB-MCA is designed to meet the stringent requirements of nuclear instrumentation and offers many distinct advantages including the following:

• Supports both of the PHA and the MCS modes in a single unit

• Excellent performance in terms of resolution, DNL, etc.

• Universal connectivity to a wide range of PCs 

• Operates from outside of a PC

• Low power consumption; works on USB bus power

• Suitable for portable as well as laboratory class instrumentation

• Easy to manufacture and use

Applications

In the PHA mode, the USB-MCA along with an external detector, spectroscopy amplifier and HV supply, can be used for gamma ray spectroscopy in the following areas:

• Isotope research

• Nuclear reactors

• Accelerators

• Health physics instrumentation

• Applications with low resolution scintillation detectors

In the MCS mode of operation, the USB-MCA along with appropriate external detector, amplifier and Mössbauer drive unit, can be used for Mössbauer spectroscopy.

Infrastructure Required for commercial production

For production

• Electronic assembly shop with PCB fabrication, testing and assembly including SMD mounting and soldering of ICs and components

• Universal device programmer for EPROM / Flash-ROM programming
  (JTAG programming cable and associated software can also be used to program Flash-PROM)

• Standard facilities for manufacturing electronic systems and boards

• Mechanical fabrication, painting, and engraving of metallic enclosure

For testing

• CRO of 100 MHz bandwidth minimum

• Precision and Sliding pulse generator type GL-3, made by BNC, USA or equivalent

• IBM compatible PC (P-4 or better) with USB 1.1 port

• HP-Ge detector system along with HV supply and spectroscopy amplifier

Manpower Required

• An electronics graduate engineer with 3-4 years experience of testing analog and digital circuits and fault finding 

• An experienced technician with 8-10 years experience for wiring and assembly of the circuits and PCB