[Solid_ec] Timing jitter

[Xiaochao Zheng]

Hi Alexandre:

Here are four lists, for the two SPDs, Preshwoer, and shower, on the timing jitter contributions that I am somewhat familiar with.   I do have questions for some of them, see below.  Mostly, how do we deal with the rise time?  If the signal has a long rise time, how do we estimate its jitter?

We can use this as a starting point of the discussion.

LASPD:

- PMT (FMPMT assembly H6614-70): rise time 2.5ns, transit time 9.5ns, TT spread for single photon 0.44ns, TT spread at the expected amplitude is <0.1ns. So maybe should use 2.5ns as the rise time and <1ns as the jitter?

- light propagation: 3ns jitter, or roughly length of LASPD divided by 2E8 m/s. This may be correctable at the trigger level by using the EC cluster position. If so, after correction there should be (cluster size)/(2E8 m/s) remain, which would be 1ns for a transverse cluster size of 20cm.  Offline should be correctable to (tracking position resolution)/(2E8 m/s), which would be at the 10s of ps level.

FASPD:
- PMT (16ch MAPMT assembly H12445-100MOD): rise time 0.52ns, transit time 5ns, TT spread for single photon 0.34ns, TT spread at the expected amplitude is <0.1ns. I am not sure what value to use, but 1 ns seems to be quite large. You could use "<1ns" for both the rise time and the jitter.

- WLS light emission: the WLS material has a 8ns of decay time. On the scope the signal rise time is more like around 12-15ns.  Not sure what jitter to use. Not correctable.

- light propagation: The signal will have 13-20ns of rise time due to propagation of WLS lights in the WLS fiber.  Here I used that the total fiber length for the 4 radial segments are between 5.1 and 8.1m, each divided into two fibers.  So the rise time would be (5.1 or 8.1)m /2 / 2E8 m/s, giving 13ns for the inner-most segments and 20ns for the out-most segments.  I don't know what value to use for the jitter. Event-by-event jitter could come from the hit position of the event in combination with how the initial photons are reflected and absorbed in the fiber, which could statistically limit the jitter to a small value, but the exact jitter estimation has to come from a detailed simulation.

Preshower:
- PMT (16-ch MAPMT assembly): same as FASPD 
- WLS light emission: same as FASPD
- light propagation: the total fiber length per module is 3.2m. Using the same estimation method I get 3.2m/2/(2E8m/s) which is about 8ns of rise time.

Shower:
- PMT (R11102): rise time 3.2ns, transit time 34ns, TT spread for single photon not listed in the catalog. I think we can use 3.2ns as the rise time and again <1ns as the jitter given the large light yield of the Shower.
- WLS light emission: same as FASPD and Preshower
- light propagation: hard to estimate. Since the light propagation is along the longitudinal direction I don't expect it to contribute to the event-to-event jitter.

On top of these you will need to add the other sources, such as those in your list (which I don't really know how to estimate):

time-walk
cable length
HV
path length/momentum
pile-up

Xiaochao

----- Original Message -----
From: "Alexandre Camsonne" <camsonne at jlab.org>
To: "Xiaochao Zheng" <xiaochao at jlab.org>
Cc: "solid ec" <solid_ec at jlab.org>
Sent: Tuesday, January 20, 2015 2:19:37 PM
Subject: Re: [Solid_ec] Timing jitter

https://userweb.jlab.org/~camsonne/SoLID/DAQ/SoLID%20timing%20jitter.pdf

https://userweb.jlab.org/~camsonne/SoLID/DAQ/SoLID%20timing%20jitter.pptx

Yes sorry, I tried to fix a carrier return but that messed up the URL.

Alexandre

On Tue, Jan 20, 2015 at 2:17 PM, Xiaochao Zheng <xiaochao at jlab.org> wrote:

> The links have a typo: SOLI->SOLID
>
> ----- Original Message -----
> From: "Alexandre Camsonne" <camsonne at jlab.org>
> To: "solid ec" <solid_ec at jlab.org>
> Sent: Tuesday, January 20, 2015 2:06:20 PM
> Subject: [Solid_ec] Timing jitter
>
> https://userweb.jlab.org/~camsonne/SoLI/DAQ/SoLID%20timing%20jitter.pdf
>
> https://userweb.jlab.org/~camsonne/SoLI/DAQ/SoLID%20timing%20jitter.pptx
>
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