Can I switch between the 78 ps (8-channel) and 156 ps (16-channel) configurations of the Logic16 unit?
- Yes, but not during a measurement. Switching between the 78 ps and 156 ps configurations requires updating the firmware of the FPGA that is housed within the Logic16 unit.
What is the maximum tunable delay that can be set between the channels?
- Delays are only positive.
- The individual delay is an 18-bit integer for each channel: (∼40 μs) using the 16-channel firmware or (∼20 μs) using the 8-channel firmware.
- Note: The delay is a multi-hit delay which can store up to 1024 events/channel. In other words, 25 MHz (50MHz) @ 40 μs (20 μs) delay – and higher rate for shorter delays.
What is the operational measurement rate?
Coincidence counting mode, in other words processing rate on the FPGA:
- 100 MHz over all channels sustained (continuous) rate
Time-tagging mode
- Without time tag filtering – approx. 10 MHz, as limited by the USB 2.0 data transfer rate
- With time tag filtering – Logic16 can process up to 200 MHz across all channels, given that the filtered rate is 10 MHz or less.
How can I record time-tags over many hours in my multi-photon experiment, without accumulating excessively large data files?
By transferring data only after a set number of tags accumulate within a given time window, one can dramatically reduce the amount of data being transferred to the host PC. The photon-triplet experiments in Phys. Rev. Lett. 118, 153602 (2017) – arxiv:1609.07508 – stored filtered time-tag data over 20 h, using Logic16 units in time-tagging mode.
If the maximum transfer rate is 10 MHz, how can I use the logic unit for time-resolved measurements with a higher rate pulsed laser?
Using the filter function with a filter width just less than the period of the laser, Logic16 will only transfer those time tags for which a detection occurred. One can use, e.g. a 80 MHz Ti-Sapphire laser, and only transfer events of interest (detection events + corresponding laser signals).
Can I simultaneously measure multiple correlations?
Yes. Logic16 pre-sifts all possible coincidences that occurred within a given time window and transfers the meta data to the PC. The PC will receive information about all possible correlations and the driver will extract only coincidences requested by the user.
What software is available? Can it be customized?
- Time Tag Explorer – test installation and operation of the Logic16. This is to be used for initial set-up trouble-shooting, but does not provide data acquisition (saving) capability.
- UQD Logic Counter – basic coincidence counting and data recording
- Customization – UQDevices suggests that experimentalists develop a customized data acquisition software in their preferred DAQ environment (LabView, C#, Matlab, etc.). If you have questions, requests or feedback regarding available software please use the [contact] page.
Does the Logic16 unit come with a power supply?
- No. The unit has an input port for a DC power supply ( 12V/≥1.5 A ) or can be powered by NIM crate (+ 12V/1A , -12V/0.5A). An example of a compatible DC power supply is here.
Can two or more Logic16 units be used together to increase the number of channels?
- Yes. One can use n x Logic16 units to effectively obtain n*15 channels.
- This is accomplished by syncing the units using a time reference signal. To do so, split a time reference signal (e.g. 1 kHz signal from a function generator) and input this reference into one channel on each unit. For example, two Logic16 units were used to employ 30 channels to time-tag a SPAD array in the following experiments: