Large A Beamsstrahlung Monitor

Readout Project

Design Reference Page

All information tentative and provided for informational reasons.

Documentation on desired features:

The LABM rates and currents are as follows:

A) There are 32 channels, initially each connected to a PMT;

B) Later connected to a Si-PMTs (incidentally, I have ordered Si-PMTs, and I will send you four as soon as they arrive).

Operational Conditions:

1) Initial SuperKEKB phase, with beam intensities 1/10 of nominal, and photomultipliers.

Photon Rates: 0.1 to 0.01 per bunch crossing (6 to 0.6 MHz photoelectron rates)
Gain for most PMTs at our common mid-plateau point is between 1 and 1.5X10^6
PMTs have a measured rise time of 4 nsec and decay time of 10 nsec.

2) Nominal SuperKEKB conditions, Si-PMT, 5760 pixels per channel, Si-PMT

Photon rates 100 to 10 per crossing, hit rates are 5GHz to 500 MHz
Gain is close to 10^5 (from Advansid)
Rise time is 1 nsec or below, decay time is 100 nsec
The signal will probably need to be differentiated.

I note that we expect to run on PMTs for a couple of years, so that your costing could very well be done on PMT electronics alone.

Further comments:

I think that, for the first two years, I will want to see the same information that John Flanagan wants to see, rate-wise.

In other words,we will be busy with detector calibration, studies of total rates, and correlations with other devices.

His device, too, has limited bunch-following capabilities, and when it comes to correlation studies we are only as fast as the slowest device.

It has become clear to me that, initially, we will be entirely dependent on EPICS for data analysis.

EPICS will allow us to broadcast rates at 10Hz, but no more.

I also suggest that we ignore signal differentiation for the time being. By the time we will be in need to differentiate, we will have clear ideas
of which kind of electronics we want, anyway.

So, to conclude:

1) no differentiation for the early electronics
2) 10 Hz histogram updating
3) I can not remember how many bunches John can follow at any given time,
but I think he can follow only one at a time. That would be suitable for
us, too.

My only doubt is that people may want to test early this device against
the BPM system, which is designed to work at 1kHz from day one (so I have
doubts only about 2), plus I need to be precise about 3)). I will talk to
John about it next week and report promptly to you.

GSV's initial thoughts:

While it may be true that comparison of a sub-set of the data with the XRM only requires modest input,
it may be possible to utilize the RITC chip and hardware histogramming to build a fuller picture of the entire orbit.

Nov. B2GM meeting time may be a good opportunity.

[UH Physics] [University of Hawaii]

Last modified: 11/13/2011