HIST Operations
The following are e-mail messages regarding the operation
of the HIST detector.
Most recent messages are at the top. Older messages are down below.
Date: Fri, 1 Nov 1996 10:24:19 -0800
From: "Al Kolasinski" <al_kolasinski@qmail2.aero.org>
To: " CEPPAD Team" <ceppad-team@lanl.gov>
Precedence: bulk
Sender: ceppad-team-request@nis.lanl.gov
As part of the IPS/HIST calibration, photomultiplier-gain check/calibration
for HIST will take place in the vicinity of apogee on 11/4/96. Normal science
output will be suspended at 19:59:50 (near apogee) so that calibration of
the
IPS and HIST can commence. Return to normal science mode will occur at
22:05:10. The HIST photomultiplier high voltage will be left at its present
value and, if necessary, reset after evaluation of the calibration data.
No
changes will be made before 11/15/96, and the Team will be notified well
in
advance of any proposed changes.
Al Kolasinski
Date: Thu, 15 Aug 1996 14:48:24 -0700
From: "Al Kolasinski" <al_kolasinski@qmail2.aero.org>
Subject: HIST operations.
To: "Jim Sullivan" <sullivan@buphy.bu.edu>
Cc: " CEPPAD Team" <ceppad-team@lanl.gov>
Precedence: bulk
Sender: ceppad-team-request@nis.lanl.gov
This is by way of an update and a mea culpa. First, the calibration I referred
to last week took place on Day 225, and I heard from Adam Contos the data
are
at BU as of today. Second (here comes mea culpa), late last week we requested
that the instrument be placed in a mode where it toggles every sixteen spins
between ABC and HBC modes in the Science portion of the data. The instrument
went into that mode at 11:58 UT today. I meant to send out a memo about
our
intent on Monday and forgot.
The rationale behind this move is that the automatic switching caused
considerable confusion and showed some apparently inexplicable effets in
the
data. It also appears that in the BC mode the instrument electron response
is
contaminated by protons because of the way the coincidence logic is
implemented in that mode. The ABC and HBC modes do not suffer from this
problem. Thus, it appeared wise to compare the instrument response in this
toggling mode over an extended time period, but with data in the two modes
accumulated at times as close to each other as possible. The future instrument
operating mode will presumably depend on what we learn from this comparison.
The data should be available early next week. We will analyze them and send
copies of comparison plots to anyone interested.
Al
Date: Mon, 5 Aug 1996 16:16:33 -0700
From: "Al Kolasinski" <al_kolasinski@qmail2.aero.org>
Subject: Change in HIST Voltage Step
To: " CEPPAD Team" <ceppad-team@lanl.gov>
Precedence: bulk
Sender: ceppad-team-request@nis.lanl.gov
REGARDING Change in HIST Voltage Step
This is by way of clarification concerning the previously announced change.
A
limited calibration had been previously done on Day 69. A replay of the
data
on the HIST GSE considerably later indicated that the gain was somewhat
low -
several channels below the canonical value of 48 - 50. A plot of the steps
indicated that one voltage step above the one prevalent at the time, would
put
the alpha peak in channel 50. The voltage was raised by one step on day
day
81. In the meantime, a careful analysis of the spectrum shape showed that
there is a broad peak centered around channel 30, which does not move with
voltage, and which tends to skew the alpha source apparent peak to lower
channels. When this "background peak is subtracted from the spectrum,
the
alpha peak moves several channels upwards. Thus, in the higher voltage step,
the peak appeared in channel 53 instead of 50. Since the instrument had
been
operating in that state for considerable time, I decided to leave it there
until another calibration, which finally took place on day 208 and was more
extensive than previous ones. Now the peak appears to have moved to Channel
57, which is 15 percent higher than the canonical value. Barring any
objections, I propose to lower the voltage by two steps, which according
to
the calibration should put the alpha peak in channel 50. Lowering the voltage
three instead of two steps would put the peak to about channel 46 or 47,
which
seems too low. I propose from now on to perform a 1 hour calibration at
apogee
once per week, and correlate the results with temperature, to get a better
picture of gain stability or lack thereof.
AlK
Date: Mon, 5 Aug 1996 13:01:25 -0700
From: "Al Kolasinski" <al_kolasinski@qmail2.aero.org>
Subject: Change in HIST High Voltage
To: " CEPPAD Team" <ceppad-team@lanl.gov>
Precedence: bulk
Sender: ceppad-team-request@nis.lanl.gov
8/5/96 11:43 AM
A calibration performed on day 208 shows that the PMT gain is 15 percent
above
its nominal value. This is to let everyone know that I am going to lower
the
PMT voltage by two steps, i.e. the HIST Command word will read 37xx instead
of
3fxx, where the value of x depends on the instrument mode. The command
sequence will be 1) run another calibration sequence, with the last step
to
correspond to 3702 Hex, and to leave the instrument in that voltage state
until further notice. The commands will be implemented in the next two to
four
days.
Al Kolasinski
Special
Announcement
Date: Wed, 17 Jul 1996 18:53:08 -0700
From: "Al Kolasinski" <al_kolasinski@qmail2.aero.org>
Subject: HIST Commands Planned for a
To: " CEPPAD Team" <ceppad-team@lanl.gov>
Precedence: bulk
Sender: ceppad-team-request@nis.lanl.gov
This is to inform everyone that a HIST PMT Gain calibration will be performed
on 7/23 or 7/24, depending on when the necessary commands get uploaded by
POC.
The calibration operation will take approximately 1 hour, and will be
performed in the vicinity of apogee. Upon completion, the instrument will
be
left in its present high voltage state pending evaluation of the calibration
results. At the end of calibration, the instrument will continue to switch
among the ABC, BC, and HBC modes according to the present criteria, and
in
addition it will be commanded to toggle between the direct event and singles
modes on major frame transitions, until further notice. This will not affect
the science portion of data acquisition, but byte 15 will contain direct
event
or singles data on alternating major frames. If there are any questions
about
or objections to this course of action, please voice them within the next
two
days or for ever hold your peace!
Al Kolasinski
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