Beam6b dropout oct11
a2010 reported that alfa beam6b had low power on
02oct11. This was seen in wapp beam6b and beam7b (which is a copy of
beam 6b). A2611 (zoa) ran after a2010 and used the mock spectrometer.
The power levels were also erratic for bm 6b .. so the problem is
not with the wapp or mock spectrometers.
the plots show the
variation of the total power in the 1450 alfa band (172 mhz) during the
a2611 observation on 03oct11 (.ps) (.pdf)
Ganesh,dana,denis, et al say that the problem
in the amplifier.
- Black is bm6a, red is bm6b.
- The power was adjusted in the mock spectrometer once before the
start of the plots.
- mock6a needed a gain of 13db
- mock6b needed a gain of 24db.. so the power was
lower by 11db in bm6b at the start.
- top: Total power vs time (hour from midnite ast) in spectrometer
counts (linear scale).
- bm6b started with no power. this caused the mock gain to be set
high for bm6b.
- around 4.6 hours, bm6b power recovered. Since the gain had been
set high at the start, there was about 11db more signal in beam6b than
- At 5.6 hours, the power in 6b started to dropout. The power
level was erratic for the rest of the observation.
- Middle: total power vs time in degrees K.
- The spikes in polA, polB are where the cal was turned on.
- Bottom: total power (degK) vs za.
- The vertical jumps are the cals turning on.