Operational Training on HPGe Detection System Bruker Baltic HPGe and MiniMCA-166 Training

1. Operational Training on HPGe Detection System Bruker Baltic HPGe and MiniMCA-166 Training

2. The HPGe Spectrometer • Based on: • Portable HPGe detector (Bruker Baltic) • Multi Channel Analyzer: MiniMCA-166 • Notebook • Software: separate programs to record and evaluate spectra • WinSPECi – detector setup and acquiring spectra • Identify – isotope identification • MGA – burn up evaluation of Plutonium • MGAU – enrichment of Uranium

3. Get started for Gamma Spectroscopy • Step 1: fill detector • Step 2: connect detector with MMCA and PC • Step 3: switch on MMCA • Step 4: start software WinSPEC for Inspectors (WinSPECi) • Step 5: select or create setup file

4. Step 1: cooling detector • Replace screw from detector with funnel • Put detector in upright position • Fill the detector (several shots) with liquid nitrogen (LN2) • Detector is full if drain releases LN2 • Wait 2 hours until detector is cooled down completely • Detector is cool for several hours • Replace funnel with screw (wait until layer of ice is gone) 1st fill 2 hours No topping Top (2nd fill) Cool for 10 hours Cool for 20 hours

5. Step 1: cooling detector LN2, several shots Funnel Detector in upright position Drain with LN2 dropping out

6. Step 1: cooling detector Hint to increase the resolution Fix the screw (safety valve) Turn detector for 180 degrees, remain for 5 -10 seconds and turn back

7. Step 2: connecting equipment • Set of cables to connect HPGe’s Preamplifier with MMCA • High Voltage cable (HV), type SHV • Signal cable (OUT), type BNC • Preamplifier power cable (DC12V), type serial RS232 • Signal test cable (TEST), type BNC (not connected) OUT DC12V HV

8. Step 3: switch on MMCA • Connect MMCA with the USB cable to the PC • Switch on MMCA – safety switch with lift function • Green LED is blinking in a high frequency • Detectors green LED should be on – indicates that detector is cool

9. Step 4: start WinSPECi software • Open program WinSPECi • Three selections before program starts • Customized preferences (select no) • Connecting MMCA to serial port* (select search and offered COM port) • Retry to connect MCA (select yes) * Physical address of the USB port

10. Step 4: start WinSPECi software

11. Step 4: start WinSPECi software

12. Step 5: detector setup SETUP Create setup file Open stored setup file Open spectrum recorded with the system Use old setup, stored in MMCA’s memory:DO NOT RESET MMCA at the start sequence

13. Step 5: create setup • To work with the system the following parameters have to be implemented • Detectors High Voltage (see manual) • Measurement time • MCA setup: amount of channels, thresholds • Amplifier: polarity, shaping time, pole zero cancellation, gain adjustment • Energy calibration to change the x-axis from channels to Energy [keV]

14. Step 5: create setup a) High Voltage for detector • Menu\setup\high voltage • High voltage: up to 3000 V • Polarity depending on hardware (HV-module) • Inhibit signal if interruption hardware is used (select Canberra HPGe)

15. Step 5: create setup b) Preset for measurement time • Menu\Setup\Presets • Measurement time in Real Time, Live Time or None • Measures until certain area or integral value Select like here

16. Step 5: create setup c) Multi Cannel Analyzer • Menu\Setup\MCA • Channels 128 – 4096 • Threshold: set to 0 % • Upper Level Discriminator (ULD) and Lower Level Discriminator (LLD) – don’t change Select like here

17. Step 5: create setup Step by step 1.) Shaping time: 2μs 2.) Input polarity: positive 3.) Pole Zero Cancellation: • Select PZC adjustmen • Place source in front of detector • Select Automatic PZC by offset minimization 4) Gain adjustment • Select visual amplifier adjustment 4. 1. 2. 3. 3a.

18. Step 5: create setup Gain adjustment: • Select the energy range for your purposes • Standard: 3000 keV with 4096 channels • Select a high energetic source, like Co-60 • Select visual amplifier adjustment and place source in front of detector • Calculate position for 1332 keV Co-60 peak: 4096 channel = 3000 keV ? channel = 1332 keV  1818 • Move cursor to the position in channel 1818 • Adjust gain (coarse and fine) until recorded Co-60 peak and cursor overlapping, quit with OK (F11)

19. Step 5: create setup Fine adjust with F4 or F5 – until overlap of peak and cursor Peak is far to the right – press F2 several time

20. Step 5: create setup • Energy calibration (fast method): X-axis is now in channel units, but we need energy units [keV] • Record a spectrum of the Co-60 source • Enter Menu/Analysis/Energy calibration and select “channel/energy pair input” and select ” Do energy calibration” • Channel 1: 0, Energy 0 • Channel 2: 1818, Energy 1332

21. Step 5: create setup Co-60 spectrum X-axis in channels

22. Step 5: create setup

23. Step 5: create setup • energy calibration with 2 sources will follow – it is more complicated by exacter

24. Error – high count rate • The red LED on the detectors preamplifier gives signal if the count rate is so high that the detector cannot work properly – move back from source until red light goes off • In case of bad vacuum in the detector the humidity inside raises and leads to a lot of signal (like high count rate) when detector fired with HV • Try to work with less HV • Send it for repair