Present at GS Chris Orth (author), Erik Katsavounidis, Ioannis
Katsavounidis, Massimo Orsini, Stefano Stalio, Lory Gray, Sophia
Kyriazopoulous
During these shift weeks there have been periods of intense work on a
couple of items (namely the WFD and LaMoSsKa) followed by absences by
about half of us present due to conferences and vacations.
Thankfully, MACRO has been pretty quiet during these lapses in
man-power -- so this shift report should be quite brief.
WFD/LaMoSsKa -- On June 3 the WFD fix was complete! Lory, Sophia, and
Chris have been running checks on the WFDs to verify that the fix is
working as expected, and to check for any cabling errors that may have
been introduced during the fix.
One surprise is an increase in the over-all data rate of about 10-15%,
noticed by Erik and Ioannis. A plot of Rate vs event number during
the entire WFD repair operation clearly shows a gradual increase in
rate. It turns out that the combination of cap values on the BU
fanout and the WFD discriminator that REDUCE the overshoot so that it
never saturates the buffer on large pulses also ENHANCE the overshoot
into the WFD discriminator on medium size pulses. This means that
every muon pulse in the WFD is followed by 3-7 usec of digitized
pedestal. The increase in rate is not drastic, and it is actually
somewhat desirable to be able to monitor the pedestal in data, so we
do not see this as a serious problem.
Starting with run014171 a modified latching scaler plus 2 lamosska
modules were installed on microvax one. Starting with run 014180 the
latching scalers and lamosska modules were installed throughout
MACRO. This is the final fix required to recover full sensitivity to
highly ionizing slow particles. The latching scalers latch the times
of lamosska triggers on each supermodule, the 106usec delayed triggers
from each supermodule, and the STOP signals from each supermodule (now
plugged into the latching scaler instead of the WFDs). The new WFD
STOP is formed from the OR of the delayed Lamosska triggers and the
ol WFD STOP from the Stop Master. For more info on changes to Camac
list and how to decode the new lamosska/latching scaler data, see posts
by Erik and Chris to the macro-general bulletin.
The Rest of MACRO
3rd Harmonic Filter
The Lab electricians tested a new 3rd Harmonic Filter throughout
MACRO. The filter interacted with the LeCroy HV supplies in a very
disturbing manner. The MACRO phototubes on SMs 3,4 and 5 began to
oscillate on and off with a period of a few seconds. The effect was
most noticable in the TOHM activity lights. We do not know the exact
nature of what caused this oscillations. Paolo tested the test LeCroy
module with a varying inductive load and could not reproduce the
effect. Paolo suspects that the interaction might be due to the
Power Stabilizers which were installed after this 3rd Harmonic Filter
was designed. Following these tests we found that at least 3 phototubes
on SMs 3-5 need to be replaced.
On Wednesday the 18th, new PALS were inserted into the rate monitor of
the CSPAM on microvax 1. The change caused a 10% increase in the rate
of MACRO due to the CSPAM rate monitor alone (and not the WFDs as one
might suspect), so the rate monitor has been commented out of the
microvax 1 camac lists until it can be fixed.
There has been some flakiness in the CAMAC highway on uvaxes 1 and 2
lately. Whenever the power is cycled on the crate holding the LeCroy
CAMAC interface on uVax 1, the LeCroy on SM2 trips off and some LED
switchboxes on SM2 turn on. On microvax 2 we saw "HV fault" messages
on the console, and again, LED switchboxes were found on. On microvax
1 it is recommended to unplug the camac interface from the SM2 LeCroy
before cycling the power on the crate holding the CAMAC interface.
On Wednesday Jun 24, Massimo upgraded the LaMoSsKas on SM1 and SM2.
They were using slower amplifiers than on the other modules and we
didn't have time to finish this upgrade on the previous Friday.
Also on Wednesday, Chris and Sophia performed some sensitivity
measurements of the tohm on boxes 1b01, 1e05, 1w12, and 1t03. Sophia
ran her analysis to compute the tohm efficiency vs. LI count and found
consistent results with the more extensive sensitivity measurements
performed following the installation of the Tohm Attico. The
sensitivity measurements performed then were for 6usec wide, very low
light pulses (about 20 spes in 6usec at the far tank end). For the
new tests we also accumulated data at different pulse widths. We hope
to gain a better understanding of the tohm efficiency near its high
beta cutoff (10^-3). More tests will be performed during our next
down-time.
This last week there have been a few crashes. On Tuesday morning
there was a fan fault on Pisa Crate 2c; the fan and power supply were
replaced by Massimo. On Friday the run was found taking data at a
very low rate. The HV to the PMTs was found off on SM6 and there was
a fan alarm on the system CAMAC crate on uvax1.
-Chris Orth
Boston University
Happy Birthday Stefano! (Jun 28, 1997)