Full list of commands available to control GS-MAX-8000

[ObinRobinson]

Hello everyone,

I have a GS-MAX-8000 and a Scionix Holland 38B57 scintillator which I am trying to set up in Becqmoni and ImpulseQT. Right now I have the voltage set to -U027 (621.9 V) and I am getting a lot of noise below 30 keV. The noise piles up so fast that I can't even see any useful spectra. How do I filter this noise out or otherwise get rid of it so I can see some useful data? Below is a screen shot of what I am seeing and this just isn't very helpful when I am trying to do spectroscopy. I know the scintillator is fine and it works perfectly when connected to my Theremino MCA. I only see this mountain of noise below 30 keV with the GS-MAX-8000. Thanks in advance.

[Rob Tayloe]

I recently spent some time using the GS-Max-8000 with a Scionix 38mm x 38mm NaI detector using the newest version (3.1.2) of ImpulseQt. I started with a Cs-137 source near the NaI detector. I adjusted the HV (using the -Uxxx command) so that the 662 keV peak was located a bit less than half way in the range of bins (channels). I was using 2048 channels to acquire data. For me this was -U032 to get 668 volts, which is less than I would normally use for this detector. It seems that there is no means for adjusting the gain. I used the pulse view, in the first tab (device setup), to see that the rise and fall settings were appropriate. I save screen captures and the csv files upon completion of a measurement. I've no idea what use I'd make of the waterfall. Shown below are two screen captures from my recent use of this NaI detector with the GS-Max-8000 and ImpulseQt -

[ObinRobinson]

Thank you for those screenshots. The GS-MAX-8000 seems to be really powerful but I am just in that uphill learning curve trying to get it calibrated. Thanks again!

[Sesselmann]

Hi Guys,

Good to see some discussion around the GS-MAX-8000 and ImpulseQT, your questions help me understand which parts need to be explained better.

Seems like you are both comfortable with using -U for adjusting the voltage up and down.

LLD Discriminator
To set the Lower Limit discriminator use the command -nos nn where nn is the number of channels. Easy to remember, just think of -nos as "noise" it essentially cuts off the lowest channels,

Rise and Fall
The next most likely setting you may need to adjust is the rise and fall, this can vary depending on the type of crystal. Using the Pulse view function you can see the sample points. When set correctly you should capture the whole pulse from baseline to baseline (see image)

Pulse Length
The GS-MAX-8000 has one trimpot, this is for adjusting the pulse length, turning the trimpot clockwise makes the pulse longer. It is usually sufficient to have between 15 (i.e. 5 rise 10 fall) and 25 total samples for NaI(Tl) but CsI(Tl) might require more.

Baseline Trim
The baseline trim should be more or less set correctly before shipping but should it requre adjusting it can be done using the command -V nn. The base line is set correctly when the pulse rise starts at zero.

Temperature compensation is a little more complicated and will require its own post.

Steven

Tab1 Max

[ObinRobinson]

Thanks so much for the reply! This is a screenshot of the pulses I am getting. I now see that it needs to be adjusted.

Is there any way of saving a specific setup? I have four different scintillators and it would be nice to have an "A, B, C, or D" configuration that I could load up rather than having to write down and re-enter the settings for each. The biggest difference is the voltage settings and I know I can set it manually for each one but it would be nice to have the noise, rise, and fall also ready to go as well.

Thanks again! The GS-MAX-8000 is really powerful! I know I'll get years of usage out of it.

[Sesselmann]

Obin,

The settings in the GS-MAX-8000 are actually stored in the hardware, the hardware only has two copies of the settings, one is an emergency backup copy.

It is possible to write a script in ImpulseQt that saves and restores the settings for multiple detectors to json, I can look at that in a future versions. pretty simple it would just loop through and send the necessary commands.

On your pulse shape image it looks like you can reduce the rise to 5 samples.

PS: Glad you like the Max, if you havent already done so, it would be great if you can leave a review.

https://www.gammaspectacular.com/blue/gs-max-8000

Steven