Commissioning of the MUON Spectrometers in ATLAS and CMS

1
Commissioning of the MUON Spectrometers in ATLAS
and CMS

• Differences and similarities between the MUON
  Spectrometer of ATLAS and CMS.
• Status of the ATLAS-MUON installation and
  Commissioning.
• Status of the CMS-MUON installation and
  Commissioning.
• General comments on readiness.
• Conclusions.

2
Different Philosophies between the 2 large
experiments

• ATLAS Philosophy
• Trigger and perform precise measurements of HE
  muons in the spectrometer, correct for losses in
  the calorimeters and improve measurement using
  inner detector for LE muons.
• Main emphasis on low mass Spectrometer and high
  coverage (etalt2.7)

• CMS Philosophy
• Main emphasis of the spectrometer is on the
  trigger (2 different and complementary systems),
  while momentum measurement is mainly based on ID
  tracking in a high magnetic field (4 Tesla).
• Main emphasis is on precise Pt measurements for
  rapidity lt1.8.

3
Different Philosophies lead also to different
importance of the ID measurement, and of the
rapidity behavior
ATLAS
CMS

• While in ATLAS, the MUON Spectrometer determines
  the P resolution for Pgt20GeV/c, in CMS the
  resolution is dominated by the ID.
• In ATLAS, the MUON Spectrometer resolution is
  dominated by the alignment and the Drift Tubes
  resolution

4
Due to the magnetic field, the 2 experiments
measure different things ATLASP, CMSPt

• In the low rapidity region CMS has a superior P
  resolution (mainly due to the high Solenoidal
  field), while at high rapidity, is the ATLAS
  spectrometer, with its toroidal field that has
  the better resolution.
• At high momenta, it is the L2 in BL2 in the
  MUON Spectrometers,that allows to recuperate the
  P resolution.
• Due to the relative importance of the MUON
  Spectrometer in ATLAS, its performance depend
  critically on
• Alignment
• Good field knowledge (due to non-uniformity)
• Good Drift Tubes Calibration

5
Status of the ATLAS-MUON installation and
Commissioning

• All barrel chambers have been installed, but not
  all are at the final position.
• Except for 40 of the EO chambers to be installed
  in May, all End-Cap chambers have been installed.
• The so called staged EE chambers have been
  constructed (thanks to Protvino) and their
  installation is foreseen after the shut-down.

6
Know the magnetic field i.e. know where the
magnets are to within a couple of mm in a
non-uniform field

• Magnet was powered in November 06 and its field
  measured and reconstructed with probes installed
  in the chambers.

7
4 coils were reconstructed in shapewith very
small residuals

• If you know (alignment) where the chambers are,
  the field reconstruction works.

8
Where are the chambers and how much do they deform

• 6,000 images in the barrel and 6,000 in the
  end-caps.
• System allows to measure
• Translations in X-Y
• Rotation
• magnification

9
Status of the barrel alignment and its Performance
Type Total Working Broken Bad because MDT not in place
Projective 117 85 12 20
Axial 1035 998 10 27
Praxial 2006 1938 6 56
Reference 256 232 4 20
CCC 260 234 10 16
BIR/BIM 32 32 0 0
Inplane 2110 2064 8 38
Total 5816 5589 50 177

• Measuring 10 to 100 micron changes, due to magnet
  heaters being turned-on.

10
Status of End-Cap Alignment

• Main reference system is the alignment bars.
• Since Wheels are not in final longitudinal place,
  no projective element has been used, however they
  have been used to align and follow the chambers
  in the azimuthal component in the Small and Big
  Wheels.

11
Operation of the End-Cap Alignment

• The alignment system has been used to correct the
  psition of the chambers in the Small and Big MUON
  Wheels.
• All its elements (except the projective part) are
  working and the chamber positions are being
  monitored continuosly

12
Status of Barrel MDT Commissioning

• Sectors from 3 to 8 Commissioned with Cosmic
  rays.
• Sectors 1-2 9-10 noise test (missing HV-PSs).
• Sectors 11-12 under test.
• List of remaining problems
• Dead tubes less than 1
• Some noisy wires mainly on BOS
• HV trips 2
• Gas leaks 18 yet unfixed leaks

13
Status of MDT-DCS Commissioning

• HV/LV monitoring of FE electronics T and V
  .
• Alignment
• Gas
• B-field
• T-sensors
• Initialization

14
Status of MDT Commissioning in the End-Caps

• Side C
• LVHV completed
• Temporary Gas connections now moving to final
• Operated under Cosmic rays in common runs.
• 3 Chambers excluded from read-out for DAQ/Fiber
  problems
• 3 Multilayers with HV Problems
• Side A
• LV fully equipped
• HV bottom half
• Temporary Gas connections on bottom half now
  moving to final
• Bottom half operated under Cosmic rays in common
  runs.
• 1 FE card excluded from read-out
• 3 of all chambers with some problem need access
  between wheels to solve them.

15
Status of MDT-CSC Commissioning in the End Caps
Small Wheels

• Small Wheels fully commissioned outside pit.
• All 3 systems have 0.05 of non-working
  channels.
• Transport through CERN has been very impressive.
• No broken wires and no gas leaks after descend to
  ATLAS pit.
• Second Wheel went down last Friday.

16
Installation and Commissioning of the EO-MDT
chambers

• All EOS chambers have been installed and
  commissioning has started.
• 9 out of the 16 mechanical Large sectors have
  been installed, with the corresponding alignment
  bars (major effort to have all components at CERN
  in mid December).
• 4 out of 16 Large sectors have been installed
  with all their chambers.
• Following ATLAS closing, remaining 7 mechanical
  Large sectors to be installed (2 per day) and the
  remaining 12 chamber sectors (1 sector per day).
• There will be very little time for commissioning
  of the large sectors.

17
Read out of MDT and Calibration

• All RODs have been installed and tested.
• Data taking is performed from the control room.
• During December run, calibration data stream has
  become operational at LV2 (only data in ROI send
  to TIER2 centers).
• Calibration performed quasi on-line, with very
  encouraging results.
• Many problems, but first results are very
  encouraging.

18
Status of RPC Commissioning

• Cabling of HV/LV Racks on HS
• 75 of the work completed
• Missing Sectors 11, 12, 13, 14
• Should be finished within 1 month (depending on
  CAEN delivery)
• Cable test and connection to Chambers
• Sectors 1-8 completely cabled
• Working on 9 and 10
• Work pace 2 Weeks/sector
• Will increase having a second team working in
  parallel

19
Status of RPC Commissioning

• Many gas leaks found due to broken gas inlets
  (80, 43 of them already repaired).
• All commissioning performed with gas circulating
  in open mode. Soon to move to recycle mode, but
  various issues need yet to be clarified.
• To complete RPC commissioning by mid June, a 2
  step procedure has been started, with the first
  step being
• Testing all cable connections and their
  correspondence checked
• DCS working and electronic threshold optimization
• HV checked and debugged
• Gas Checked and debugged
• Trigger electronics and front end electronics
  debugged and timed.
• The remaining problems are left to a second pass.
• With this procedure, expect to achieve 1 sector/2
  weeks.

20
Status of RPC Commissioning

• Sectors 1-6 have been commissioned with cosmics,
  while 7-8 are being completed now.
• The number of problems left is small
• Dead strips 0.2
• Disconnected gaps for HV problems 0.6
• Disconnected gaps for Gas Leak 0.2
• Noisy channels few units
• Average Noise 0.4 Hz/cm2

MDT -RPC Correlation
? 9 mm
Distance between MDT track and RPC cluster
21
Status of TGC Commissioning

• All sectors tested with cosmics either in surface
  or in the pit Bad Channels 10-4
• 6/24 sectors operated during common runs
• CAEN Power supply and crates delivery have been
  the main bottleneck
• Installing mini-crates and AC/DC converters
• Difficult access for TGC3 Need BW away from EO
  for ½ of the sectors (2 Weeks of work in parallel
  with EO installation).
• TGC currently operated with CO2 in a temporary
  Gas distribution System - Need urgently to move
  to Final Gas System
• Distribution racks (final connection to racks
  being performed now)
• Final mixture (n-pentane) problems have been
  found with the heaters used to performed the
  mixture. Expect to be solved in April.

22
Status of TGC Commissioning

• Both trigger and readout paths are operational.
• All readout and trigger electronics are
  installed.
• Trigger Latency measured 86-90 clk

23
Remaining problems

• Although the CAEN delivery problem is under
  control (last delivery in April), there are still
  some problems with failure rates.
• Cruising speed to commission the RPC system
  should be increased (doubled) in order to
  complete the first pass by end of May.
• One needs to move soon to a gas recirculation
  system for RPCs, and in particular optimize the
  various filters.
• One needs to start the commissioning of the TGC
  gas system with CO2 and ensure that the final
  system will be available in May.
• The available time to complete the power supplies
  installation for the Low-Pt trigger in the TGCs
  (TGC2-3) is very tight (2 weeks in parallel to EO
  installation).
• The time for the completion of the EOL
  installation is very tight (2 weeks), which will
  not allow much time for full commissioning.

24
The CMS muon system
Barrel Drift Tubes (DT) (4 layers)
Resistive Plate Chambers (RPC) (6 layers)

End caps Cathode Strip Chambers (CSC) (4
layers) Resistive Plate
Chambers (RPC) (4 layers)
25
CMS muon detectors
DT
CSC
RPC
26
Barrel wheel
27
End cap disks with CSCs
22 Jan 08
28
A Measurement ! Magnet Test and Cosmic Challenge
MTCC on the Surface Cosmic muons charge ratio
(?/?-) (Awaiting definitive alignment constants)
MTCC on the Surface Cosmic muons momentum
distribution)
29
Commissioning DT
system in UX
Entrance Angles
30
Examples of Performance DT
Analysis of Drift-Tube commissioning data for
Wheel 0, sector 10. Resolution 300?m from
cosmic muons
31
November Global Run

• 100 of HB
• 50 of HF, HE
• 20 of DT, HO
• 10 of barrel RPC, EB (for a few days)
• 0.04 of strip tracker (6 module RIB prototype)
• Synchronized
• 10M events logged
• Small of End-Caps detectors took part
  underground, due to Power Supplies delivery

Airshower triggered by RPC DT segments
reconstructed at HLT
32
General Comments on readiness

• Both MUON systems have been delayed in their
  commissioning by the late arrival of CAEN Power
  Supplies, which should be completed by May-08.
• In the case of ATLAS, being the MUONs the
  outermost detector, their installation and their
  services were always the last one.
• The RPC gas recirculation system has encountered
  many problems, not all yet solved, which have
  slow down the commissioning due to the high cost
  of gas.

33
Conclusions

• The MUON systems of the 2 large LHC experiments,
  with 1,000s of M2 detectors and over 1M
  readout channels each, to measure the passage of
  the particles with resolutions of less than
  100microns, constitute one of the major
  technological defies ever achieved.
• The two experiments are well advanced in their
  commissioning aspects, and the fact that one is
  already taking cosmic data from their respective
  control room, a few months before beam is a very
  good sign.
• Albeit many problems, the two large LHC
  experiments will be able to take MUON data with a
  large part of their systems at the beginning of
  the LHC beam.