Experimental equipment interacting with beam operation D. Macina TS/LEA Many thanks to my colleagues both from the experiments and the machine for their fundamental input to this talk Workshop Chamonix XV: January 2006

General considerations Hardware, software and procedures are implemented according to our PRESENTLY BEST knowledge of what the operation of the machine and experimental devices will look like However, the real challenge in the operation of these devices will become clear only when the machine will be operational Therefore, it is very important to keep flexibility in the actual implementation of the hardware, software and procedures

Overview: magnets TOTEM / CMS ALICELHCb ATLAS DIPOLE SolenoidBarrel Toroid L3 Solenoid CMSCMS LHCbLHCb ATLAS ALICEALICE Solenoid EC Toroid

Magnets operation Dipoles will distort the beam orbit and their effect has to be compensated locally with dedicated compensation magnets. Therefore, their operation is tightly related to beam operation –All experimental dipoles will be operated by the machine and ramped with energy Solenoids create couplings and orbit distortions that, in some cases, may have to be compensated during beam operation: –ATLAS and CMS solenoids (and toroids) will be operated by the experiments themselves (at least during the first years of operation) –ALICE proposes that the machine operates all its magnets (the solenoid in addition to the dipole) The status of all magnets will be monitored in the CCC (information sent via the DIP protocol) Beam interlocks may be implemented if needed A procedure on the magnets operation needs to be established and agreed between the experiments and the machine

Overview: movable detectors TOTEM / CMS ALICELHCb ATLAS LHCb ATLAS ALICE ZDC Roman Pot TOTEM Roman Pot VELO

ALICE ZDC Located at 116 m from IP2 Used during HI runs to measure: –centrality of the collision –absolute luminosity ZP may be used during pp runs to study diffractive physics IP2 ZN ZP

Injection The ZDC is at garage position Collisions established (or before, i.e. during ADJUST mode) 1) the ZDC are positioned at the theoretical beam level 2) vertical fine adjustment may be needed to center the two calorimeters at the beam level ZDC operation Garage position (20 cm below the beam level) Injection: to protect the calorimeters from possible beam losses Whenever data taking is not needed to minimise the absorbed dose Data taking position (at beam level)

Interaction with the LHC machine during operation (1) LHC vacuum chamber (located outside vacuum chamber => no direct interaction with the beam) anticollision switches top cover ZP ZN ~ 3 mm

Interaction with the LHC machine during operation (2) The technology has been chosen recently ZN only used in HI runs ~10-20 % I just in front of ZN does not spoil the energy measurement. The effect on the measurement of the impact position of the particles is presently under study The compatibility with the ZN depends on the amount of converter necessary for the luminosity monitor. If NOT compatible: –Place converter on movable support –Use ZN to monitor luminosity (and to bring beams into collision) D2 TCTH ZN ZP Luminosity Monitor Luminosity monitor IP2

ZDC operation ALICE has agreed to be responsible for the positioning of the ZDC during beam operation The LHC machine is fully responsible for the zone where the ZDC is located Interaction with the Luminosity Monitor operation only during HI run: if Luminosity Monitor’s absorber not compatible with ZN, we have backup solutions compatible with both the ZN and the LHC machine operation

VErtex LOcator Pile up VETO Modules Interaction region VELO is located in the LHCb cavern VELO consists of two halves which move in the horizontal plane to reach the final position, i.e. 5 mm from beam axis ( ~ 70 σ from beam axis at  * = 10 m) Technically, VELO is able to touch the beam VELO has a fast precise standalone tracking system and it is able to locate vertices with a precision of ~ 10 μm in the transverse plane in a fraction of a second

VELO: operation VELO will be operated by the LHCb collaboration At injection VELO is in the open position (3.5 cm from beam axis) For the VELO operation, LHCb will use an online monitoring which is able to reconstruct the collision vertices (and therefore the luminous region) with very high precision In general, VELO will not move if there are no collisions It takes about 5 minutes to go back from the data taking position to the garage position Radiation monitors located close to VELO are under study. Their effectiveness in detecting dangerous situations during collisions (like beam too close/scraping the VELO vacuum shield) has still to be demonstrated When in UNSTABLE BEAM Mode, the operator should always keep in mind that VELO is not in the GARAGE. On the other hand, since the repositioning of VELO will introduce some dead time in the data taking, future experience will tell if it is really necessary to move VELO when in UNSTABLE BEAM Mode

Roman Pots Located in the IR5 (IR1) tunnel The pot will approach the beam at a distance of ~ 10  to measure elastic and diffractive protons TOTEM XRP station consists of 4 pots moving in the vertical plane and two pots moving in the horizontal plane ATLAS XRP station consists of 4 pots moving in the vertical plane TOTEM XRP station

Roman Pot: operation (TOTEM) Injection: RP is in the open position (4 cm from beam axis) Stable beam: RP starts to move: –Initial information on the beam position is given by the BPMs integrated & located close to the RP stations –The pots move by <= 35 mm (resolvers and LVDT) watching the signal from BLM (their effectiveness still to be demonstrated, even if very useful at the SPS test) –The vertical pots are centered around the beam axis using the on-line data from the detectors located inside the pots and equalizing the data-rate. Additional information from the positioning system will be used too –10 σ distance is carefully reached watching BLM (real distance will be dictated by the machine running conditions) –Then the horizontal pot is moved in using a similar procedure –Once data taking is started, a MOVEMENT_INHIBIT will be switched on (TOTEM proposal under discussion with the MPWG) –Roman Pot commissioning will be initially done without detectors (BLM calibration) and later with detectors (radiation monitor and scaler rates vs BLM)

Roman Pot: safety The nominal distance from beam axis is 10 σ. Technically, the RP is able to touch the beam Therefore, safety is a very important issue: –The Collimator Control System has to ensure that the Roman pots are always in the shadow of the collimators for safety reasons => the Collimation Control System and the Roman Pots Control System have to be integrated/linked together –Experiments agree to operate RP from the CCC (good communication between the CCC and the experiments fundamental) –Initial contact between the Collimator Control Group and the experiments held in October However, no big progress since then…

Conclusions and remarks Magnets: all dipoles and ALICE solenoid operated by the machine. ATLAS and CMS magnets operated by the experiments. Detailed procedures on their operation to be agreed in the coming year ALICE ZDC: operation for data taking done from the ALICE Control Room. However, machine is fully responsible for the zone where the ZDC is located VELO: operated by the LHCb Control Room. Effectiveness of the radiation monitors under study Roman Pot: –Operated from the CCC –Functional specifications on their operation has been prepared by TOTEM and presently under discussion –A major work has still to be done on the integration of the RP Control System with the Collimation Control System