Timestamp of photon arrival times

I would like to make a measure of cross-correlation of two photons.  Auto hardware correlators and crossed correlators are available, but expensive.  It seems that many other users resulted in the idea of using the 80 or clocks 100 MHz in the counter of entry for each desired channel, starting the counters at the same time and get every channel of photons in the door of the corresponding counter.  Each photon triggers so the meter to store the total of the clock in its internal register, that is, the time stamp for this photon. Since then carries on a 32-bit counter clocked at 100 MHz only occur every 42 seconds, and average rate of photons will be at least 100 Hz, excesses should be easily recognized and corrected in post processing.  So assume that all we have to do is get meter reads in a buffer.  Bursts of photons with separations of arrival can be as small as few clock cycles.  Average rates may be a few hundred kHz or more on each channel.  We can adjust this rate by turning the power of the laser to the top or to the bottom - the source for the broadcaster that produces the stream of correlated photons.  I suspect many others would like to know which system is better for these types of measures, the 6602 or the X-Series.  If FPGA is a good solution, perhaps we should start a new thread about it.  But for 6602 or X-Series: what is the fastest, it can do so for short bursts (speed for how long) and what is the sustainable rate?  I realize that the sustained rate will depend on the material.  I thought I only saw that the PXI beats the PCI bus in this type of application.  PXI versions are better?  In particular, what are the effects of the FIFO 128 sample on the X-Series compared to the 2 on 6602 buffer solution.  And I noticed something about the speed of the front end for these two choices could be a problem in this regard.  Pulses (photon) TTL on the door will have a width of 10 to 50 nsec.

For the flow of the series X is going to be much faster than the 6602 mainly due to the FIFO aboard (but PCIe gives more throughput than PCI).  PCI or PXI should have the same flow (and PCIe vs SMU would also have the same flow).

Forum user (and NOT used) Andrew S displayed some X series streaming of references here.  On a single meter, it was able to maintain the sampling frequency of ~ 20 MHz on PCIe X Series and ~ 8 MHz on USB of the X series.  6602 benchmarks are much lower, somewhere between 200 and 300 kHz (although the system used for benchmarks is old enough).

The 6602 allows shorter pulses that the X series.  The specifications page indicates a minimum of 6.25 the 6602 ns pulse width.  I saw a specified number directly to the X series in fact.  X series devices include a maximum external base of 25 MHz clock frequency, which assuming duty cycle 50% would be 20 ns high and low times.  50 nsec would certainly long enough of a pulse, but 10 ns * could * be pushing.  You will probably need to do some tests to confirm or not the X series is able to detect all the impulses for your configuration - if not then I would suggest the X series (PCIe-6320 is the lowest cost one) on the 6602.

Best regards

Tags: NI Hardware

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