[neutron-mc] depannage manip - a typical case

[Bernhard Frick]

8/3/99

Bernhard Frick -> Jose Dianoux
cc: T. Heidemann, A. Leadbetter, P. Leconte

In the following  I will shortly summarize a loss of 16 hours
experimental time with a dilution fridge on IN16 which happend yesterday
, April.7th,1999.
In my opinion it is a typical case, which shows, that the solutions for
instrument break-downs out of working hours as proposed in the DS/DPT
meeting - at which I have assisted by chance - do not work. ( as well
for security questions).

Monday: about 17:15      Chopper 1 on IN16 is stopped
                                        as usual I try to restart, but
becomes soon clear that this does not work
about 17:30
                                        I phone F. Descamps ( as was
told in the meeting: phone the chefs)- the secretary tells me he is on
travel
                                        phone C. Gomez (mechanique
chopper)- but he is no longer at ILL;
                                        same for J.J.Vernier
(responsable REFU) and T. Mary
                                        I call the instrument technician
O. Losserand who is still here and we try to find out why the REFU
                                        does not want to reset
                                        we check all securities, cables
etc
 some time later:
                                        phone at ILL the chef in the
hierarchy above (T. Heidemann; sorry Tony, only to annoy you)
                                        get some private phone number
from the reactor ( one of the numbers turns out to be a hotel phone)
                                        try to contact P. Thomas at
home( on travel as well),

                                        The dilution fridge is at 200mK
and we want really not loose all night of such an expensive experiment.

                                        we open the REFU -  note that we
pass the limits of what we are allowed to do from security reasons
                                        The secretary of the electronics
group finds one person from electronics.
                                        He passes but he is no expert in
REFU and Choppers
                                        We decide to check two fuses on
the low tension part of the REFU - note severe security problem !!
                                        we change a broken fuse but  it
breaks immediately again

At this point we decide that we have to wait for the next day.

                                        We try to run the experiment
without background chopper, but the data are very bad.

Thus we lost 16 hours of beam time -  or about 40 - 50kF. How expensive
would be an 'astreinte' ?

The first thing on next morning was of course that we were critisised by
one of the experts, that we should not open the REFU. With some right he
asks the question what would happen if somebody had an accident during
this intervention.

The REFU problem was solved on next morning within an hour.


Bernhard Frick





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