The CMS Outer HCAL SiPM Upgrade.

Transcription

1 The CMS Outer HCAL SiPM Upgrade. Artur Lobanov on behalf of the CMS collaboration DESY Hamburg CALOR 2014, Gießen, 7th April 2014

2 Outline > CMS Hadron Outer Calorimeter > Commissioning > Cosmic data Artur Lobanov DESY CALOR 2014 Page 2

3 Hadron Outer Calorimeter > Meant to correct MET and jets > Consists of scintillator tiles with wavelength shifting fibres. > Ring 0 has two layers, Rings ±1&2 have one. Artur Lobanov DESY CALOR 2014 Page 3

4 HO within CMS CMS DETECTOR Total weight : 14,000 tonnes Overall diameter : 15.0 m Overall length : 28.7 m Magnetic field : 3.8 T STEEL RETURN YOKE 12,500 tonnes SILICON TRACKERS Pixel (0x150 μm) ~16m2 ~66M channels Microstrips (80x180 μm) ~200m2 ~9.6M channels SUPERCONDUCTING SOLENOID Niobium titanium coil carrying ~18,000A MUON CHAMBERS Barrel: 250 Drift Tube, 480 Resistive Plate Chambers Endcaps: 468 Cathode Strip, 432 Resistive Plate Chambers PRESHOWER Silicon strips ~16m2 ~137,000 channels FORWARD CALORIMETER Steel + Quartz fibres ~2,000 Channels CRYSTAL ELECTROMAGNETIC CALORIMETER (ECAL) ~76,000 scintillating PbWO4 crystals HADRON CALORIMETER (HCAL) Brass + Plastic scintillator ~7,000 channels Artur Lobanov DESY CALOR 2014 Page 4

5 HO within CMS Artur Lobanov DESY CALOR 2014 Page 4

6 HO Front End Readout Upgrade Hybrid Photo Diode (HPD) HO used HPDs to detect the scintillation light as all HCAL, but they are not optimal for the HO conditions: > Problems with running in fringe field of the CMS magnet > Low gain and photo detection efficiency > Ageing Because of these problems CMS has decided to replace the HPD sensors with Silicon Photo Multiplier (SiPM) sensors. SiPM mounting board Artur Lobanov DESY CALOR 2014 Page 5

7 HO Upgrade Plan R&D Production burn-in, QC installation commissioning till / / /2014 > The upgrade design has been validated during the last years in laboratory, test-beam, and on the detector > Installation and commissioning of installed SiPMs. > Validation of installation and calibration with cosmic muons. Artur Lobanov DESY CALOR 2014 Page 6

8 SiPM Commissioning Quality Control Strategy After HPDs are replaced with SiPMs the following happens: > Communication test to verify slow control and all channels are responding > Measurement and optimisation of SiPM operation variables: Artur Lobanov DESY CALOR 2014 Page 7

9 SiPM Commissioning Optimisation parameters: > Temperature > Gain > Pedestal > LED signal > The SiPM temperature is controlled by a Peltier element > Working point 0.3V, to lower power consumption, but still be flexible. > Each SiPM at its own temperature SiPM Temperatue [deg C] SiPM temperature vs Peltier Voltage CMS Preliminary V Peltier [V] Artur Lobanov DESY CALOR 2014 Page 8

10 SiPM Commissioning Optimisation parameters: > Temperature > Gain > Pedestal > LED signal > SiPM gain adjusted by operating voltage > Gain is measured using Single Photo-Electron (SPE) peaks next to the pedestal > All channels are set up to have gain around 6 ADC/pe [to prevent ADC from saturation] Artur Lobanov DESY CALOR 2014 Page 8

11 SiPM Commissioning Optimisation parameters: > Pedestal is set to 9 ADC counts per 25ns (1 LHC TimeSlice[TS]) for all channels > For 4 TS this gives approx. 36 ADC > Temperature > Gain > Pedestal > LED signal Artur Lobanov DESY CALOR 2014 Page 8

12 SiPM Commissioning Optimisation parameters: > Temperature > Gain > Pedestal > LED signal > LED light is used to monitor stability of the SiPMs outside of collisions > SiPM-fibre light coupling in Ring 0 and Rings 1&2 differ and thus the LED amplitude has to be adjusted differently Artur Lobanov DESY CALOR 2014 Page 8

13 Outline > CMS Hadron Outer Calorimeter > Commissioning > Cosmic data Artur Lobanov DESY CALOR 2014 Page 9

14 Cosmic muons with HO HO cosmic setup > CMS is located 0m underground, but has a 20m wide shaft > Now CMS is in open position. > Some wheels are under shaft, allowing muons to come straight from the surface. Cosmics analysis motivation: > Validation: verify the correct cabling in eta-phi map > Calibration: extract MIP values for all channels >... Artur Lobanov DESY CALOR 2014 Page

15 Cosmic muons with HO HO cosmic setup > CMS is located 0m underground, but has a 20m wide shaft > Now CMS is in open position. > Some wheels are under shaft, allowing muons to come straight from the surface. Trigger setup HO only! > Each wheel is divided in 4 quadrants > Trigger threshold 40 ADC counts per 1TS > Coincidence between any top sector (1,2) with any bottom sector (3,4) > 1TS delay between top and bottom Artur Lobanov DESY CALOR 2014 Page

16 iphi Trigger rates map Shaft Trigger rates per eta-phi (248.8) (189. Ring 1 Layer 1 Ring 2 Layer CMS Preliminary 8 > Higher 430.9rate observed in ( horizontal (426.0) tiles under Hz shaft Table 2: HO tile dimensions along for different rings and layers. The tile sizes, whic 0.25 ring boundaries, are mentioned in brackets. iphi = Shaft iphi = 71 4 Ring+2 Ring 0 Ring+1 Ring-1 Ring-2 iphi = ieta Trigger rate for each individual channel iphi = Figure 8: Layout of all the HO trays in the overall CMS detect Figure 8 shows the final layout of all the HO trays in the overall CMS detector.length 6 Artur Lobanov DESY CALOR 2014 Page 11

17 MIP extraction > Signal is summed up for 4 time slices [TS] and measured in ADC counts. > Muon MIP value is the Most Probable Value (MPV) of a Landau-Gauss convoluted fit of the signal distribution. event fraction SiPM dark noise spectrum after pedestal subtraction CMS Preliminary Hz 4 3 Signal spectrum after pedestal subtraction CMS Preliminary Most Probable Value from fit: MPV = 86.6 ADC ADC ADC SiPM noise rates Single channel signal spectrum with coincidence trigger Artur Lobanov DESY CALOR 2014 Page 12

18 MPV map > MPV values won t be uniform because of several factors: > Rings 1,2/0 have 1/2 scintillator layer/s > Light transmitting fibres length vary > Scintillator tiles have different sizes light collection efficiency varies iphi Eta vs. Phi MPV CMS Preliminary MPV ieta MPV value of each channel Artur Lobanov DESY CALOR 2014 Page 13 0

19 Muon track angle correction Problem > Muon signal gets altered because of different track path lengths in tile. > MIP distribution gets shifted. > Signal has to be corrected by the cosine of the muon track incidence angle. Solution > Each event the muon track is build for the two tiles with highest signal. > Cos(track,tile) is computed and the signal values of the two tiles are corrected. Muon track through CMS Artur Lobanov DESY CALOR 2014 Page 14

20 Muon track angle correction Muon track entry point projection 1 CMS Preliminary x and y are coordinates of the muon track vector projection on the horizontal plane x,y = 0 corresponds to a vertical muon x-projection (arb.units) y-projection (arb.units) HO Muon entry point shifted because of shaft 1 Artur Lobanov DESY CALOR 2014 Page 15

21 Muon track angle correction cosmic muon incidence ~normal to scintillator Not corrected for path-length Signal Path-length corrected Signal CMS Preliminary > MIP distributions with and without path-length corrections in a horizontal tile ADC cosmic muon incidence ~parallel to scintillator Not corrected for path-length Signal Path-length corrected Signal CMS Preliminary ADC > In a vertical tile: de-smearing and shift of MPV value with respect to horizontal tile signal. Removed after applying path-length corrections. Artur Lobanov DESY CALOR 2014 Page 16

22 Uncorrected/path-length corrected MPV vs phi in Rings 1,2 > MPV values are more uniform after path-length correction > The remaining non-uniformity is due to different length of fibres, which connect the SiPMs to the scintillating tiles. MPV MPV vs. iphi CMS Preliminary MPV values Path-length corrected MPV Uncorrected MPV iphi Artur Lobanov DESY CALOR 2014 Page 17

23 Cosmic data > From the cabling point all sectors within a wheel are the same, so an averaged MPV can be calculated for a single sector. > Each Readout Box is connected to 12 iphi sectors in rings-1,2. > One can clearly see the location of the readout modules and the decrease to the sides. > Decrease in ieta is due to the fibre length inside the scintillator > Decrease in phi is due to the fibre length outside (farther away from SiPM) MPV MPV averaged over all readout boxes in Ring-1 1 CMS Preliminary ieta phi Artur Lobanov DESY CALOR 2014 Page 18

24 Cosmic data Summary > HO has been upgraded with SiPMs > Commissioning of fresh front-end readout ongoing > Validation and calibration with cosmic muons proven possible Future plans > Global Run analysis with Muon systems > Calibration with pp-collision data > Muon trigger with RPC Muon system Artur Lobanov DESY CALOR 2014 Page 19

25 End. Artur Lobanov DESY CALOR 2014 Page 20

26 Backup Backup Artur Lobanov DESY CALOR 2014 Page 21

27 Hadron Outer Calorimeter > HCAL Barrel (HB) is not thick enough to fully contain hadronic showers > Needed to extend HCAL outside the solenoid magnet and make additional sampling of the shower. > This part outside the magnet is the Hadron Outer Calorimeter (HO). > Consists of scintillator tiles with wavelength shifting fibres. > Ring 0 has two layers, rings ±1&2 has one. Artur Lobanov DESY CALOR 2014 Page 22

28 HO Front End Readout Optical decoder unit (ODU) Readout Module > Optical decoder unit (ODU) routes fibres form one projective tower to one readout channel. > Light has to be read out by a photo detector... Artur Lobanov DESY CALOR 2014 Page 23

29 SiPM Description SiPM > array of µm APD pixels > pixels operated in Geiger mode > common readout: signal = fired Q pix > quantised output signal easy gain calibration > maximal measurable photon flux is function f(n pix, pix ) need to control saturation > temperature dependant gain > radiation sensitive Artur Lobanov DESY CALOR 2014 Page 24

30 HO Readout Module Artur Lobanov DESY CALOR 2014 Page 25

31 HO Upgrade Plan HO SiPM upgrade plan: > The system design has been validated during the last years in laboratory, test-beam, and on the detector > HPD replacement designed as a drop-in existing RMs and electrical/optical coupling reused, only HPD replaced by SiPM card-pack. > Installation and commissioning of installed RMs. > Validation of installation and calibration with cosmic muons. R & D production burn in, QC installation remove RM from detector replace HPD with SiPM QC of re furbished RM install RM into detector QC of installed RM Artur Lobanov DESY CALOR 2014 Page 26

32 HO Layout > HO is located in all 5 barrel wheels of CMS and is split in 30 iη sections along the Z-axis (beam-pipe). > In the transverse plane HO consists of 12 sectors à 6 trays and is split thereby in 72 iφ sections. > Each iη iφ tile is read-out by a separate channels making 2160 physical channels. > In addition, some readout modules [RM] have several dark channels for noise measurements and calibration. Each of the 2376 channels has to be tested. iphi = 71 4 Ring+2 iphi = Ring+1 Ring 0 Ring-1 iphi = Ring-2 Layout of all the HO trays in the overall CMS detector iphi = Artur Lobanov DESY CALOR 2014 Page 27