Section C - problems with TRIPS.

A TRIP is caused when some part of the CTD (usually a group of sense wires close to the beam) has a higher than usual current, even for an instant, usually due to increased background.

The hardware stops data taking within one microsecond, and the HV supplies for the sectors of the CTD affected are switched off. About one second later the supplies for the rest of the CTD HV begin ramping down to STANDBY (if they were in an HVON state). This rampdown takes about one minute.

Normally after all the CTD reaches STANDBY voltages (i.e. between about 20 volts and 40 volts) the trips are auotomatically cleared by the program. The HV channels which were tripped are auotomatically switched on again, and the channels which were off rise towards STANDBY voltages. You should then wait about 30 seconds to a minute till all the voltages on the dav display read about 40/20/30 volts. (Ignore "You may now type HVON" - this message is obsolete). Then, if it is thought that the backgrounds are O.K. and there are no other known problems, type

hvon

to begin ramping up to the HVON state again (which takes about 1 minute). When the CTD HV program is sure that all parts of the ctd are at their proper working voltages the state changes to

CTD HV ALL ON : O.K.

and data taking can resume. If the rampdown from HVON to STANDBY never finishes (it should not take more than about 1 minute) it may be that some part of the electronic hardware or HV control program has HUNG (see section D).

If once the rampdown to STANDBY has been finished the trips do not clear auotomatically, type:

clear
on the keyboard and wait for a few seconds to see if trips clear successfully. If this is unsuccessful try typing
clear
again.
If this is also unsuccessful try typing
off
to go from the STANDBY state to the OFF state (this takes about 1 minute). Then when the OFF state has been reached, type
clear
and see if trips clear. If still unsuccessful, a program reload is probably required, go to section D.
If trips are cleared successfully, but the HV will not ramp up to HVON again, see section B.
if the program repeatedly trips either during HV ramping up, or very soon (a few minutes) after reaching HVON
perhaps the HERA background is too high
check that the HERA collimators are in the correct position and that HERA is otherwise operating normally.
check that ZEUS & H1 LPS are at the right position if inserted and that HERA-B wires are "normal".
if this state of repeated trips has developed slowly over several hours and no other malfunction can be seen, it is worth checking that the CTD gas supply (in the gas room on level 8) is O.K.
Has the ethane run out?
Has the alcohol run out?
As a last resort you should try exiting and reloading the CTD HV program - see section D.

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