The Operation of the LHC detectors

1. The Operation of the LHC detectors LPCC student lectures CERN June 29th 2010 Special thanks to T. Camporesi, C. Garabatos Cuadrado, T. Pauly, W. Kozanecki, S. Wenig Lectures prepared by: T. Camporezi, C. Clément, C. Garabatos Cuadrado, R. Jacobsson, Luca Malgeri, T. Pauly LHC Lectures – Experiment Operation

2. Experimental Control Rooms ATLAS ALICE CMS LHCb LHC Lectures – Experiment Operation

3. Experimental Control Rooms ATLAS ALICE Why do we need experimental control rooms? CMS LHCb LHC Lectures – Experiment Operation

4. Experimental Control Rooms • Experimental control rooms are far from the detector, due to the radiation environment. • 1) Monitor and maintain a large industrial complex: electrical systems, cryogenics, gas systems, radiation environment, access restrictions, safety of personel ad equipments • 2) Operate and monitor the experiment to maximize performance for physics • Operate to maximize quality of data being taken • Operate at maximum data taking efficiency LHC Lectures – Experiment Operation

5. Example of Control Room Layout Infrastructure, safety, access... Trigger and DAQ Tracking Detectors EM Cal, HCal endcap Muon Chambers HCal shift leader Luminosity Beam conditions Manned by shifters 24/7 + experts on-call for each specific task + how many experts and shifters required? LHC Lectures – Experiment Operation

6. Example of Control Room Layout Data Quality Monitoring Event Display Trigger Busy Monitoring Run Plan Detector Status Trigger Rates LHC Status Data Acquisition Status, Global record and trigger rates, trigger setup... LHC Lectures – Experiment Operation

7. Accelerator / Experiment Cycle Beam Dump Squeeze, adjust Physics Physics Stable beam Declared Magnet Current Ramp Ramp Down Injection The Activity in the experiments is paced by the LHC machine cycle The shift leader makes sure that the entire detector follows this scheme, gets ready on time, .... LHC Lectures – Experiment Operation

8. Beam Modes LHC Lectures – Experiment Operation

9. Prepare for Injection Christophe Clement LHC Lectures – Experiment Operation

10. Accelerator / Experiment Cycle 6 3 4 5 Beam Dump Squeeze, adjust Physics Physics 7 2 Stable beam Declared Magnet Current Ramp Ramp Down 1 Injection 1 Prepare experiment for injection! Finish all ongoing activities: calibrations, tests, stop playing! LHC Lectures – Experiment Operation

11. Injection Handshake b/w LHC and Experiments operators Big warning sound a la Star Trek When LHC is warning of INJECTION LHC waits for the experiments to be READY Go To SAFE mode at INJECTION WARNING VETO LHC Lectures – Experiment Operation

12. Experiments STANDBY ATLAS • Every experiment has sensitive equipment • that needs to go into a safe mode before injection, eg. • ATLAS • Silicon tracking (pixel, SCT) detectors • Muon Chambers (reduced HV) • CMS • Silicon tracking detectors (pixel, strip)= OFF • Muon Chambers (reduced HV) • The Zero Degree and CASTOR Calorimeters • In this state the LHC team can inject "pilot bunch" • - 450 GeV, one low intensity bunch No bias voltage on the Pixel • Low bias voltage on the SCT • Low HV on Muon system SAFE for the experiments ≠ SAFE for the machine UNSAFE for machine=> I> 1012p @ 450GeV UNSAFE for the experiments *much* earlier Experiment SAFE => IN STANDBY LHC Lectures – Experiment Operation

13. Eg. ALICE Super-safe/Safe/Eeady states Each detector defines the conditions for each state Transitions between states controlled by one single command super-safe, safe => STANDBY LHC Lectures – Experiment Operation

14. Christophe Clement LHC Lectures – Experiment Operation

15. PILOT BEAM • Currents in magnets can only change at a certain rate • Higher energy beam is more stiff • −> In case of wrong steering of the beam there is time for the system to react and • dump the beam (Beam Loss Monitors) • Potentially most dangerous for experiments is initial injection of bunches at 450 GeV • If wrong magnet settings from start or • Combination of hardware problem, bad readings, bad settings... • In this case no warning, if a train of bunches is extracted from SPS, • Could potentially shoot many bunches directly into sensitive experimental equipment • => first injection in an empty machine is done with pilot bunch LHC Lectures – Experiment Operation

16. Extreme Cases for Illustration Wrong setting of MCBX Wrong setting of D1 not up-to-date with latest machine settings.... illustration only! MCBX and MCBXA are the inner triplet orbit correctors for the LHC, MCBX (Horizontal-Vertical Dipole Correctors) MCBXA (with nested Sextupole-Dodecapole insert) Christophe Clement LHC Lectures – Experiment Operation

17. Example: ATLAS Beam Conditions Monitor 38 cm 183cm 4 BCM stations on each side of the Pixel detector • Diamond detectors • Mounted on Pixel support structure at z = +/- 183.8 cm and r = 5.5 cm • Each station: 1 cm2 detector element + front-end analogue readout • Can generate a beam dump LHC Lectures – Experiment Operation

18. Completion of Injection Handshake All Experiments in a safe mode=> All experiments READY LHC can inject LHC Lectures – Experiment Operation

19. Eg. Injection Handshake in ALICE Detectors in safe state Injection handshake just started Christophe Clement LHC Lectures – Experiment Operation

20. Injection Permit • SAFETY Hardware signal, if FALSE, injection is not permitted • LHC experiments can set it to TRUE or FALSE • For safety of the experiments, the LHC cannot inject unless it is TRUE • At the end of the handshake procedure it is set to true to the experiments • It is set to FALSE at the end of injection to avoid • eg. injection during ramp or stable beam ATLAS Injection Permit Key If Injection permit is removed beam is not dumped Only "pausing injection" Christophe Clement LHC Lectures – Experiment Operation

21. Injection of probe beam 5 109 protons / bunch LHC Lectures – Experiment Operation

22. Accelerator / Experiment Cycle 6 3 4 5 Beam Dump Squeeze, adjust Physics Physics 7 2 Stable beam Declared Magnet Current Ramp Ramp Down 1 Injection 1 • Once beam is injected and circulating, one can start data taking in a "dummy mode" • Purpose: make sure data flow is in perfect shape (ATLAS) • Cannot be used for physics since: • No collisions, • Some detectors partially off • Special (robust) trigger setup LHC Lectures – Experiment Operation

23. Trigger scheme before physics The ATLAS trigger has 3 levels Level 1 = hardware trigger, readout up to 100kHz Level 2 = readout up to ~3kHz Event Filter = readout typically O(200Hz), limited by Tier 0 and offline capability Trigger menu defined by: Trigger items, algorithms, chains Prescales (PS) Level 1 Trigger L1_EM5 L1 PS a trigger chain L2_g10_loose Level 2 Trigger L2 PS EF_g10_loose Event Filter LHC Lectures – Experiment Operation

24. ATLAS Trigger scheme before physics By changing prescale one can effectively turn off or on a trigger chain The trigger menu for physics is uploaded at the start of data taking right after injection Use special prescale sets before stable beam - eg. no algorithm using tracks can be run (silicon tracking detectors in STANDBY) - in practice only some Level 1 trigger items are running Trigger menu cannot be changed without stopping the data taking and reconfiguring the DAQ and trigger systems Prescales can be changed while only pausing the triggers, new luminosity block. LHC Lectures – Experiment Operation

25. Energy Ramp 6 3 4 5 Beam Dump Squeeze, adjust Physics Physics 7 2 Stable beam Declared Magnet Current Ramp Ramp Down 1 Injection 2 During the Ramp, the LHC clock frequency changes with time Effect on the detector electronic Some experiments doing calibrations during ramps LHC Lectures – Experiment Operation

26. Experiments during LHC Ramps Example of trial ramps (LHC dry run in 2009) Clock Frequency (Hz) During LHC Ramps experimental electronics see varying clock frequency Can sometimes lead to desynchronisation Depending on experiment: => Do not issue triggers during the steepest part of the ramp, up to ~2.7 TeV per beam => Do not run during ramp => Automatic in ATLAS, special application listening to the LHC BEAM MODE If BEAM MODE=RAMP => do not issue any triggers If Magnet currents > 2.7 TeV, resume triggers (automatic) LHC Lectures – Experiment Operation

27. ALICE Calibration runs during LHC ramp-up or flat top Calibration runs during LHC ramp-down (or adjust) LHC Lectures – Experiment Operation

28. End of Ramp Up 6 3 4 5 Beam Dump Squeeze, adjust Physics Physics 7 2 Stable beam Declared Magnet Current Ramp Ramp Down 1 Injection 3 End of ramp: the energy is not changing anymore, but beam is not stable yet LHC operators might squeeze, adjust, carry out various operations Maintain the experimental equipment in STANDBY. LHC Lectures – Experiment Operation

29. LHC Page-1 Accelerator: Beam Modes If strange – coded (in units of 120 MeV) BUNCHED BEAM INT. FBCT Fast Beam Current Transformer I(B1) – I(B2) TOTAL BEAM INT. DCCT DC Current Transf. Coupling of Beam Permits  LHC ready to receive beam  Intensity < Safe Beam limit  Intensity > 2 109  Roman Pots allowed in  Physics  Post Mortem Signal  LHC Lectures – Experiment Operation Christophe Clement

30. Collapse beam separation Experiment Can monitor the two beams brought into collisions Beam 2 Side Beam 1 Side Beam positions Beam angles LHC Lectures – Experiment Operation