Transcript ELQA and other issues

ELQA and other issues
 ELQA @ 20K, without temperature stabilization?
– Introduced to localize suspected faults easier
– Making use of the remaining resistance
– Mechanically equal to cold conditions
– Gas density is lower than at cold => only reduced voltage possible
 What did we find
– Nothing
 Could we use another methode @ cold
HC, 11.07.07, KHM-AT-MEL
– Yes, TOF I (almost) independend of the temperature
 Recommendation: Skip
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ELQA and other issues
 ELQA @ cold, when?
– To check at final voltage level no bubbles
– Superfluid
– Supercritical only at reduced voltage
– Continuity check possible at any time
– Tunnel is long, hence work has to be organized
– Other constrains (el. Safety) to be considered: Power converters off for
the DFB, busbar assembly under investigation. (UTE C 18-510)
HC, 11.07.07, KHM-AT-MEL
 Do not try to accelerate electrical check out; It may cost us
dearly.
 Note ELQA is a check, if a circuit/component is conform.
Localizing is a service to the owner(s), which we may be
unable to provide in future, once we have to test several
sectors at the same time!
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ELQA and other issues
 ELQA for 450 GeV only?
– Cui bene?
– Continuity has to be done nevertheless
• i.e. transport of equipment has to be done
• Connections have to be done/undone
• Power converters have to “consigne” and “de-consigne”
– Time saving is minimal if the HV test is skipped
 Considerable time (~30%) saving possible if we skip the
HC, 11.07.07, KHM-AT-MEL
tracing down of the exact position of the fault. (See previous
slide!)
 Proposal: ELQA tests the voltage withstand. If not nominal
MPP&HCC decide if acceptable. ELQA team will normally not
try to track the fault down.
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ELQA and other issues
 Pigtail & Busbars, enough signals?
– Experience with the D2, Q4 puzzle showed that indeed a voltage tap is
missing between pigtail/busbar and magnet
– Two v-taps connected to the top of the LTS @ current lead
– One of them could be rerouted further down without loss of redundancy
(some electronics headache still to be sorted out)
HC, 11.07.07, KHM-AT-MEL
 Lot of work involved, should be done in case of repair
–
Open DFB
–
Open lower joint
–
Extract CL
–
Undo VT onnection
–
Pull wire through flexible
–
Insert CL
–
Reconnect……….
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