Calibration 20140212 BCALComments

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Date: Tue, 28 Jan 2014 12:39:09 -0500
From: Elton Smith <>
To: Zisis Papandreou <>, Sean Dobbs <>,
     Yi Qiang <>, "" <>
Subject: [Halld-cal] comments to BCAL calibration

Hi Zisis,

Here are some belated comments to your document GlueX-doc-2379. I notice
I made my comments on the version on Dec 17 and there is an updated
version. In a  cursory glance I did not the changes, but I could be
providing redundant suggestions.

General: It is good to have the GlueX-doc number at the top. My hard
copy lacked this and it took me a while to find where I got the document.

Th first table (conditions parameters) contains very similar information
to what may be included in online data bases. These are still under
discussion, so the two need to be designed together so that they
complement each other and minimize duplication. For example, the SiPM
bias voltages will be recorded and monitored by EPICS and I don't know
how this information will be needed beyond that.

LED_cntl_clock, LED_cntl_width, LED_bias
There are a total of 32 independent pulsers (16 upstream, 16
downstream). Each of 4 pulses are duplicated 12 times and delivered to
quadrants, up or down.
I assume the clock is the rate at which the pulser is pulsed.

These next two are clearly DAQ settings and would be part of the
configuration files
ADC_threshold. Is this the same as the pedestal subtracted for the
trigger? Is it a sparcification threshold?
TDC_threshold. Is this the discriminator threshold?

The next will be recorded and monitored by EPICs
SPM_bias_lv. There are a total of 48 independent channels (24 +5V, 24
-5V). Each channel serves 4 readout assemblies on one side.
N2_flow. At the moment we do not monitor the N2 flow, they are visual
flow meters. However, we do monitor temp and humidity inside the readout

This information should be set in a configuration file
COOLING_temp - I assume this is the set point for the chiller? This
would be the temperature of the water in the cooling loop

The following information should be monitored and controlled from EPICS
SPM_temp - There is one RTD temperature probe on each cooling plate,
i.e. 96.
Readout assembly temperature and humidity. There are 8 probes (4
upstream, 4 downstream) in the air (N2) volume of the readout
assemblies. They measure temperature and humidity, so the dew point can
be calculated.
HALLD_humidity - There is only discussion at the moment to add a probe
to determine the general conditions of the hall.

Table 2 (Calibration constants)

I assume we need an offset and gain for each ADC channel is related to
the ADC_...._position and width information.   While I agree that there
may be different methods of determining the gain (cosmics, pulser,
physics, etc), I think we probably want to store somewhere the "best
estimate" of the actual gain information for each ADC channel. The
procedure for determining this value is yet to be determined and may use
several of the inputs so far mentioned.

ADC_gain 1536 channels
ADC_offset: 1536 channels
ADC_time_offset: 1152 channels

For the ADC_physics
What is meant to the ADC_physics_position or TDC_physics_position, etc
values? The intent is to use pi0 and eta production to extract the
information. However, these will not yield a single peak, but rather pi0
peaks will be determined using combination of two showers (each shower
with multiple ADC channel). From this a  procedure will have to be
developed to determine the gains of each channel.

For the TDC_physics_
What would be used for the source of this information?

Thanks, Elton.