Maintenance
at HERA
M. Bieler, DESY
WAO, Shonan, March 2003

DESY
HERA
Operations Schedule
MaintenanceHamburg, Germany

HERA(Hadron - Electron - Ring - Accelerator)

HERA is an electron - proton collider for high energy physics.
Two rings in one tunnel, 6 km circumference.
Proton ring (superconducting):
40 - 920 GeV beam energy (factor 23 in energy!)
100 mA beam current
180 bunches

Electron/Positron ring (normalconducting):
12 - 27.5 GeV beam energy
50 mA beam current
189 bunches
60 % spin polarization

4 Experiments:
ZEUS: e - p collisions (structure of protons, quarks,…)
H1: e - p collisions (structure of protons, quarks,…)
Hermes: epolarized gas target (proton spin)

HERA-B: pwire target (C-P violation)

DayIn HERA we have two accelerators, 6.3km each, with
1500 superconducting magnets
2500 normalconducting magnets
1220 magnet power supplies
16 klystrons (500MHz), 1MW output each
2 transmitters (52MHz)
4 transmitters (208MHz)
500 normalconducting cavity cells with 82 couplers
80 superconducting cavity cells with 16 couplers
550 beam position monitors
470 beam loss monitors
a quench protection system with 20 000 cable connections…

HERA Efficiency
HERA is operated 24 hours per day, 7 days per week, 8 - 11 month per year.

HERA Efficiency 2000

Idle
8%Fault
18%
p-Injection
10%

Lumirun57%

e-Injection
7%

Operational Efficiency
Efficiency = Lumi Time / Scheduled Operation TimeHERA 2000 Efficiency
0.8
0.7
0.6

Efficiency

0.5
0.4
0.3
0.2
0.10January

February

March

April

Mai

Juni

Juli

Why "only" 60% efficiency?
Both HERA and it's preaccelerator PETRA are slow cycling machines:

at least 2 hours from beam dump to luminosity

AugustScheduled MaintenanceOne maintenance day every first Thursday of the month:

Preliminary HERA Schedule 2003
Status of 3/11/2003 13:01

Startup 2003

Begin
2-Jan-03

Days
6End
8-Jan-03

Luminosity Operation

8-Jan-03

29

6-Feb-03

Maintenance day

6-Feb-03

17-Feb-03

Luminosity Operation

7-Feb-03

1017-Feb-03

Polarization Studies

17-Feb-03

14

3-Mar-03

Shut Down

3-Mar-03

126

7-Jul-03

Start-up

7-Jul-03

713-Jul-03

Machine Studies

13-Jul-03

1427-Jul-03

Polarization Studies

27-Jul-03

117-Aug-03

Maintenance day

7-Aug-03

18-Aug-03

Luminosity Operation

8-Aug-03

274-Sep-03

Maintenance day

4-Sep-03

15-Sep-03

Luminosity Operation

5-Sep-03

272-Oct-03

Maintenance day

2-Oct-03

13-Oct-03

Luminosity Operation

3-Oct-03

346-Nov-03

Maintenance day

6-Nov-03

17-Nov-03

Luminosity Operation

7-Nov-03

274-Dec-03

Maintenance day

4-Dec-03

15-Dec-03

Luminosity Operation

5-Dec-031015-Dec-03

Machine Studies

15-Dec-03

722-Dec-03

Shut Down

22-Dec-03

145-Jan-04

Maintenance Days
Access to the tunnel from 6:00AM to 3:00PM
Afterwards:

Tunnel search
Switch on magnets,…

Access to the experiments from 6:00AM to 10:00PM
Maintenance days are used forRegular service:- Fire titan sublimation pumps- Regenerate NEG pumps-…
Preventive maintenance:- Clean feedthroughs on superconducting magnets- Check magnets and RF for water leaks- Check basic functions of the radiation safety interlock- Operate relays in alarm circuits every 3 month-…
Repairs
New installations"Tunnel Tourism"

Maintenance Days
Work in the tunnel has to be announced to the technical coordinator.
Work in the tunnel is planned ahead and published on a web page:
Whereis the work done

Whois doing the work

Whatis doneProblems during Maintenance Days
Usually there is more work going on than we have on the list.
Someone shuts off the cooling water without notice.
Someone puts equipment in the line of sight for the survey.
Someone performs a test of the 'Emergency Off' buttons.
Too many people want to enter a section of the tunnel where
only temporary access is foreseen (6 keys only).

Usually some components can not be switched onafter a maintenance day
Unplugged or broken cables, components being switched off,
remote controls being switched to 'local',…..

Now it is useful to have a list of the work that was foreseen
and a list of the people that were in the tunnel.
This helps to locate a groundfault in a 6.3km dipole magnet circuit.

If something breaks unexpectedly:- most cases are handled by the shift crew:
All power supply failures are handled by the two electricians on shift.
The mixture of people from different groups on shift helps to solve
almost all other problems without external help.
- Several groups have people on call:
Quench Protection
VacuumRFSuperconducting Cavities
Power Distribution (10kV)
Cooling Water
These people give advice on the phone,login to their computer systems from homeor come to DESY and help to solve the problem.
- Shift leaders do not hesitate to call also people who are not 'On Call'(and most of them do respond…)

If a quick repair is impossible(broken magnet, broken power cable,…):- the repair is scheduled for the next workday,
HERA can in most cases still deliver e- only or p+ onlyfor calibration runs.

- Some work scheduled for the next maintenance day is donein parallel to the repair(only necessary repairs, no preventive maintenance)If something breaks unexpectedly, decisions are taken by- the shift leader in agreement withthe physicist on shift
the shift leaders of the 4 detectors
the technical coordinator of HERA
the coordinator of HERA
the director of the machine department
There is no automatic escalation foreseen, especially no deadline.