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The Low Background Beta counting systems (PC based) manufactured by NUCLEONIX essentially consits of the following constituent units.
• Mini Bin MB403& Powersupply PS401
• High Voltage Units(Two Nos)-HV 502
• Coincidence Unit UC570
• Dual Counter Timer- CD542B
• Plastic scintillator based main
& guard counter.
• Lead Shielding Enclosure
The two High Voltage Units of this counting system are used for biasing the Guard counter and Main counter respectively. Outputs from these counters are routed through paralysis time units. These output signals from paral ysis time units are then fed to the coincidence unit for obtaining both coincidence and Anti-Coincidence outputs which are inturn fed to the Dual counter timer unit.
This system is very useful in estimating gross beta activity in environmental samples and samples of low specific beta activity. The twin advantages of low background and high efficiecny offers excellent sensitivity for this counting system.
Brief specifications of individual constituent units are given as follows.
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1. Mini Bin (MB 403):
MINIM INSTRUMENTATION BIN is a standard Minibin designed to power Standard Nuclear Instrumentation Modules with 24-pin type of power connectors.
It provides mounting space for 8 standard module widths of the 8 ¾ inch high type. The eight corresponding module connectors are provided with necessary wiring for distribution of all standard power supply voltages, +/-12V & +/-24V DC.
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2. Power supply (PS 401):
Operating Voltage : 230V ac, 50Hz
Out put Voltage : +12V @2A, -12V@2A
Regulation (Line & Load) : 0.05% from no load to full load.
Ripple : Less than 3mV peak to peak at full load.
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3. High Voltage Unit (HV 502):
Output Voltage :
0V to 1500V continuously variable by a ten turn helipot provided on front panel. (All specifications are valid from 10V to 1500V).
Output Current :
It can deliver upto a maximum of 1mA.
Line & Load Regualtion :
Better than 0.005% of full scale.
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4. CoIncidence Unit UC570:
This unit is a two bit module which receives the output pulses from both guard and main counters converts these singals to TTL levels and checks for coincidence and anti-co-incidence condition to give both outputs i.e., anti-co-incidence output is released if there is output due to main counter only and there is no guard counter output with 150msec on its occurance. Also if guard counter output comes first, then futher upto 600msec any output coming from the main counter will be treated as co-incidence event. Output(s) from this unit are counted in a Dual counter timer.
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5. Dual Counter Timer :
Count Input(s) IN1 & IN2 :
100mV to 10V, unipolar or positive bipolar semi-gaussian pulse
Pulse Width:
0.5 micro sec (min)
Polarity :
Positive or Negative
Input Impedance :
5.0 K ohms
Input Counts Capacity :
999999 counts
Input Frequency (max) :
1 MHz
Pulse Height Discrimination :
100mV - 10V by a trimpot provided (inside) on PCB
Counts Indication :
12 x 2 dotmatrix LCD display
Modes of Data Acquisition :
a. Counts for a preset time
b. CPS
c. CPM
TIMER: Preset Time Setting :
Programmable through tactile switch control buttons
Control Buttons :
START, STOP, PROG, STORE, INC, DEC
Preset Time/Elapsed Time Indication:
On 12 x 2 LCD Dot matrix display
Preset Time Range :
1 to 9999
Printer Port :
Built-in
Serial Port :
RS 232C built-in
Additional Options:(at extra cost) :
(a). Data communication Software for down loading of data can be given at extra cost.
(b). Printer.
Module connector :
Amphenol Connector Type : 26-159-24P-H (24 Pin Type) or NIM Standard as per AEC specifications TID 20893 (Rev) Type : AMP 204186-5
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6. Plastic scintillator based Beta Counter
Main Counter :
Operating Voltage : 900 - 1000V
Sensitive Area : 28mm Ø
Efficiency : Better than 40% with Sr90
Energy range : 50keV to 3 MeV
Calibration Accuracy : +/- 15% with Sr90
Background (with 80mm shielding) : < 2 CPM (Auto-coincidence mode)
Guard Counter:
Operating Voltage : 900 - 1000V
Sensitive Area : 50mm Ø
Background (Inside the shield) : < 50 cpm
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7. Lead Shielding Enclosure:
This lead shielding enclosure with openable door arrangement facilitates the user to load the samples and also provides good shielding with 80mm thickness lead shield, so as to achieve very low background of the order of less than 2CPM. |
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