We have had a vacuum problem in the ring and therefore have no
beam for the next several hours.
On the abs side: we took out the dissociator, as agreed yesterday.
The outer surface of the inner tube was again very dirty, with a rather
thick black deposit. After discussion it was decided to take the glychol
out of the cooling fluid, which means having to run with a "bad" thermal
coupling between nozzle and tube and therefore at higher temperature.
While we know temperature is a factor for wall recombination effects we
also realize that the nikhef abs was running with water only as a cooling
agent and hence the glass tube T>0 C. We will run the water chiller temp.
as low as possible (5-10 C). Also, in the dissociator we put in a pyrex
tube, as in amsterdam/hermes.
Vitaly will come this evening to start up and tune the abs. We agreed on
the procedure: turn on discharge at minimum power and then start cool
down. We should be able to reach a colder nozzle temperature. At some
point the abs intensity will show a turn around (around 70 K). Hopefully
we will reach past that turn around point (say, 60K). Set the nozzle
PID controller to T_max. Measure intensity. Turn on the 02 flow (<0.5%,
maybe 0.1-0.2%) and see if there is any effect on the Rfon-Rfoff signal
as a function of time, as the ice layer builds. Then turn up RF power
to 300 W.
Then we should have a last chance a data taking, with low holding field
(50 gauss, please check) and the MFT off, and BLAST field at 3000 A
-- tancredi
________________________________________________________________________________
Tancredi Botto, phone: +1-617-253-9204 mobile: +1-978-490-4124
research scientist MIT/Bates, 21 Manning Av Middleton MA, 01949
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