07-05-2018 10:03 AM
For my photon counting experiment, I would like to sample data at the highest possible sampling rate a digitizer can achieve and for a given maximum acquisition time delta=1 second. In this case PXIe-5160 Part Number: 782621-01
Appreciate all your valuable inputs.
Thanks - Asukumari
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07-05-2018 10:11 AM - edited 07-05-2018 10:16 AM
Depending on your count rate you can use multiple buffer aquisition. The rearming of the trigger takes some time (ns), but you save memory during no counts. And if you can estinate the photon arrival time (in syncwith the pulse generator?) even better 🙂
07-05-2018 10:18 AM - edited 07-05-2018 10:21 AM
Hello again Henrik, hope you are doing well.
When you said count rate, you mean sampling rate/speed ? If yes then I have decided to go with the aggregate sampling rate of ~1.00GS/s/Channel instead of full rate (2.5GS/s/Ch).
Multiple buffer acquisition meaning circular buffer system like this ? I'm trying to find whitepaper/examples of the same to learn more.
Photon arrival time will be at a repetition rate of 10(Hz) to 100 KHz (max). How is this related to multiple buffer acquisition ?
- AS
07-05-2018 10:33 AM - edited 07-05-2018 10:34 AM
Count rate of your photons (10Hz to 100kHz)
I expect that you want the energy of the pulse 😉
See NI-Scope manual for multi record aquisition and the shipped example (modular instr./NI-scope/continous...) . Say you need 1k samples for your pulse (ok add another 1k, say 2k samples 😉 ) at 2.5GHz samplerate , you can trigger with your pulse generator (and even use pretrigger samples or delay) and capture only the part during the photon arrival . The internal memory is split into chuck of your sample bursts and not wasted to measure the dark current 😄
07-05-2018 02:02 PM - edited 07-05-2018 02:04 PM
I apologize, I guess I misunderstood about what you meant by count rate of photons. Let me explain what I am trying to achieve using a simple timing diagram.
What you described is exactly what I am trying to achieve:
07-05-2018 02:55 PM - edited 07-05-2018 02:57 PM
07-06-2018 04:38 AM - edited 07-06-2018 04:41 AM
If you want to capture all contnious samples you run into the problems you noted and you need to throw money on it. (More fast memory , or more cards reading sequential , or ...)
Please tell me more about your experiment.
I assume you have an exitation (stimulus pulse with a repetition rate 10Hz to 100kHz) and want to record the response .
Is the response a single even or short burst of photons? Is the timing deterministic after the stimulus?
How long is one photon pulse (~2µs?) and if more the photon burst ?
If there is only a single pulse of 1-2µs I would configure the scope card to trigger on and capture only that pulse (with some more samples before and after) ... and 2µs at 2GHz leads to 2k samples 😉 3µs @2.5GHz is 7.5k samples followed by a deadtime for rearming the trigger and reading the configured pretrigger points .
Can you post one or more typical 1ms dataframes ?
07-06-2018 08:06 AM - edited 07-06-2018 08:16 AM
Hello Henrik,
If you want to capture all contnious samples you run into the problems you noted and you need to throw money on it. (More fast memory , or more cards reading sequential , or ...)
When you say 'all continuous' - my goal is only to capture between a start-stop trigger for 1ms. So based on the math I provided, all continuous samples should fall within 3MB of data which I think the digitizer can handle very easily. Did I get this concept right?
Please tell me more about your experiment.
I assume you have an exitation (stimulus pulse with a repetition rate 10Hz to 100kHz) and want to record the response .
Yes you are correct. Excitation (stimuli pulse) is a burst of 5 or 10 pulses @ 10Hz rate (for simplicity sake) and I want to record the response.
Is the response a single even or short burst of photons? Is the timing deterministic after the stimulus?
Short burst of photons. Timing starts when excitation pulse is sent.
How long is one photon pulse (~2µs?) and if more the photon burst ?
Sorry, I am not sure I understand your question but if more photon burst they overlap on each other giving a higher amplitude. See the figure below, photon fall on each pixel.
If there is only a single pulse of 1-2µs I would configure the scope card to trigger on and capture only that pulse (with some more samples before and after) ... and 2µs at 2GHz leads to 2k samples 3µs @2.5GHz is 7.5k samples followed by a deadtime for rearming the trigger and reading the configured pretrigger points .
Yes, the problem is I don't exactly know how many pulses will occur therefore I want to digitize everything within a given time window. 1ms @ 2.5GHz leads to 2.5MSampels. Each sample represented by 16-bits = 2.5M x 16-bit = 40 MB of data. I think the digitizer with 64MB onboard memory should be capable of handling this with a single start-stop trigger event. Am I right?
Can you post one or more typical 1ms dataframes ?
I do not have any dataframes collected to show yet.
07-06-2018 08:41 AM
So configure a triggered multi record aquisition , each record with 2.5Msample length
start with the shipped exampe
niScope EX Multi Record Fetch More Than Available Memory.vi
or
niScope EX Multi Record.vi
modify the trigger according to your needs. (digital or externel from your pulse source)
put that into a producer consumer architecture (scope as producer) have a look at the HWS vis too
07-06-2018 08:45 AM
Thank you very much.
I was planning to architect a producer-consumer design methodology but thought its best to save data with TDMS format after reviewing certain NI whitepapers. Do you still wish me to try HWS? I don't see any support for HWS on MATLAB or Mathematica. It will be difficult to analyze data later on isn't it.
- AS