Extremely fast analogue switch

[Someone]

There are very few details available though.

6 years work, 100ps resolution.

[lazaraza]

What an impressive feedback!

Thank you all, and sorry for Mon-Tue are very packed. Later today I'll have a chance to answer the relevant questions and re-join the discussion.

[tggzzz]

Are you making something like this maybe?

There are very few details available though.

I do wish people would stop talking in only analogies and would also give simple hard information.

I hate it when news reports give lengths or volumes in terms of double-decker busses[1] or olympic-sized swimming pools[2].

[1] exception: sinkholes opening up in Manchester roads, where it is entirely appropriate and "double-deckers" has been the unofficial size unit for decades

[2] when describing the size of our latest aircraft(less) carriers, I it would have been delicious black humour if its volume volume had been given in terms of swimming pools

[coppice]

[2] when describing the size of our latest aircraft(less) carriers, I it would have been delicious black humour if its volume volume had been given in terms of swimming pools

Wouldn't it be more amusing to describe them in terms of how many jet fighters you could fit into one, if only you had some?

[tggzzz]

[2] when describing the size of our latest aircraft(less) carriers, I it would have been delicious black humour if its volume volume had been given in terms of swimming pools

Wouldn't it be more amusing to describe them in terms of how many jet fighters you could fit into one, if only you had some?

Even if we could get them, it isn't clear they could fly from them. Never mind, the French will lend us a carrier and aircraft, and I'm sure they'll enjoy the weather in the South Atlantic.

But this is getting too far off topic.

[tggzzz]

You may be able to gather some useful info from http://www.ohwr.org/projects/mrpc-25x18-24strip

"The Multigap RPC is a high precision timing and tracking detector with an active area of 25.6cm x 18.2cm and readout with 24 strips. Charged particles ionise gas in gaps between glass plates in a stack. A large electric field causes small avalanches of ionisation in each gap. The moving charges are picked up on readout strips and the timing of the charge deposition is to be read out on each side of each strip. The differential timing of the ionisation reveals the position along the strip and the precise arrival time of the particle. Multiple MRPCs can be used to measure particle time of flight (ToF). "

[lazaraza]

So, I'm back.
Finally had the time to go in details through your suggestions, but I am afraid useful as they all are, I find them not perfectly appropriate (pardon my french).

The project is sciency indeed, as much as it is developed by scientists (HEPPhys are just working on the detector part), but there is strong chance for commercialisation, and I am not sure how much details I can disclose.

To start with, the readily available lab suited solutions will not work. The system I am developing, except the much lower price, needs to be autonomous, provide incessant operation and be extremely rugged. E. g. shock resistant and to operate in >40 C  constant ambient temperatures. Each channel (2xPMT) should fit in a toothpaste tube, (if it could fit in the tube tap, the better... but I guess that is too much to ask )

@daqq,

Are you making something like this maybe?

maybe, it is too hard to tell 

@Marco, the reference to TI's TDC7200 is very nice, what worries me is the minimum time between STAR/STOP1 pulse of 12 ns, and between STOP1/STOP2 67 ns (?!?) even if the resolution could be as good as 55 ps, still the necessity of introducing so much delay will bring additional uncertainty that I try to avoid.

Bellow, I will post a schematic of my intentions in order to reply to all those questions regarding the functionality.

What must the master switch do with the signal?

He wants to switch the signal from the lagging PMT, which can be either one, through the delay line.

And then? What is the final goal? Does that switch need to measure the time differences? Some other processing?

If the goal is to measure the delays between pulses and use low cost (off the shelve) hardware then I'd look at CERN's White Rabbit project and their FMC carrier boards. ...

Yep, the goal is to measure the time difference in the interval 0.3-10 ns. No other processing at this stage than determining which pulse comes first. Thanks for the suggestion.
Will need to go more thoroughly through this WR project before commenting it.

Attached is the conceptual schematic of the FE, signal is completely asynchronous so I need to trigger on the lead PMT it could have rep-rate of MHz to mHz (mega to milli). From left to right: PMT, Comparator with hysteresis (ADCMP582 used as a Schmitt) splitter buffer (SB - ADCLK9xx), Master Switch (MSw) which sets the logic configuration of a cross-point switch (CPSw) the lead signal is set to enable SAMPLE of the S&H, the second signal goes through a delay as a HOLD, the delay is to compensate for the lag in the SAMPLE switch (1-2 ns).

[Someone]

So, I'm back.
Finally had the time to go in details through your suggestions, but I am afraid useful as they all are, I find them not perfectly appropriate (pardon my french).

The project is sciency indeed, as much as it is developed by scientists (HEPPhys are just working on the detector part), but there is strong chance for commercialisation, and I am not sure how much details I can disclose.

Then you can go back and stop mining the public for commercially valuable help. Expecting a magic solution to be handed to you is absurd, and then expecting to keep the details private for commercial reasons is not going to encourage support.

Many designs will look feasible until they reach some impossible sub system or characteristic which was not foreseen in the earlier broad design stages, it seems you've reached such a point, this is entirely normal and you backtrack and follow other architectures or designs. When working in R&D most of the work ends in failure, its those failures that are extraordinarily valuable just from the time and expense spent in determining that they dont work (that others would have to repeat to find out).

For those outside the industry high energy physics research is abound with brute force solutions as the experimentalists keep pushing the boundaries of whats possible always wanting that extra factor of 2-3 at any expense. You can find massively parallel systems built for millions of dollars that get used for a few years and then replaced. its a great field to work in if you enjoy extensive modelling to prove the solutions will work before funding is committed.

[Someone]

And for those who have worked in the industry a quick shot of when the marketing department gets it right (there is a companion mug I also have with the physics targeted graphics on it).

[tggzzz]

The project is sciency indeed, as much as it is developed by scientists (HEPPhys are just working on the detector part), but there is strong chance for commercialisation, and I am not sure how much details I can disclose.

I wish you had mentioned that earlier, so that we could have agreed my consultancy fee. To whom should I send the bill?

[Marco]

@Marco, the reference to TI's TDC7200 is very nice, what worries me is the minimum time between STAR/STOP1 pulse of 12 ns, and between STOP1/STOP2 67 ns (?!?) even if the resolution could be as good as 55 ps, still the necessity of introducing so much delay will bring additional uncertainty that I try to avoid.

That was Nico, I suggested using the CTMU in PICs, ala this. I don't know how much initial delay it needs for accurate measurement, but it's going to be a hell of a lot less than 12ns. Half the serpentine microstrip on his PCB represents is enough delay for the time->amplitude converter in the CTMU to get linear, because that's his initial calibration point, I'd estimate around 2ns. Unfortunately it's limited to 1.1 Msps on it's ADC and you'd lose a bit of that synchronizing with the CTMU so MHz repetition rates are a lost cause.

TDC-GPX can do MHz sampling rates, but that's an expensive IC. If you want to build it down to price you'll probably have to design your own Time to Amplitude converter (which honestly doesn't seem that hard given your relatively relaxed resolution target).

Yep, the goal is to measure the time difference in the interval 0.3-10 ns. No other processing at this stage than determining which pulse comes first. Thanks for the suggestion.
Will need to go more thoroughly through this WR project before commenting it.

I also suggested not switching the signals through the delay line at all, but just have two delay lines. Lets say you use 3ns of delay (part of which you would want to be able to bypass for calibration). Just put two 3ns delay lines on your PCB and split the signals, measure the delay between [signal1, signal2+3ns] and [signal2, signal1+3ns]. By combining the two results you can determine which came first. You are no longer bound by the minimum difference between the pulses, like with your switching solution. This can measure delays between the pulses down to the resolution limit of your time to digital converters, this to me seems a commercially valuable feature.

PS. probably easier to just AND the two undelayed signals (with Schottky diodes to keep it cheap) for a single start signal and measure the time of the two delayed signals.

PPS. on second thought, that decreases your resolution so maybe the first idea was better