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Jens Frangenheim [email protected] III. Physikalisches Institut A RWTH Aachen University. CMS Upgrade Workshop at FNAL, 2008/11/19 to 2008/11/21 Muon Detector Working Group, Thursday, 2008/11/20 09:40. Specific interests of German groups. Hardware development

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Jens Frangenheim

[email protected]

III. Physikalisches Institut A

RWTH Aachen University

CMS Upgrade Workshop at FNAL, 2008/11/19 to 2008/11/21Muon Detector Working Group, Thursday, 2008/11/20 09:40

Specific interests

of German groups

Hardware development

for a scintillator based MTT

  • General detector development plans

  • Aachen IIIA / IIIB and DESY collaboration

  • Associated work

  • First steps

general detector development plans

muon system+ absorption by calorimeter and coil

- tracks affected by multiple scattering

+ redundancy given by RPCs

tracker- huge number of tracks

+ precise pt measurement (high resolution, less material, strong B-field)

Muon fast Track Tag

idea: Bologna

muon tag

use a new part of muon system (MTT) to select an interesting region in the tracker in L1-trigger


one option:

use scintillator based MTT


by A. Montanari

also Aachen III, DESY

in addition to Bologna

general detector development plans

MTT design – German focus

based on the MTT idea including dimensions develop

scintillator detector

CMS Upgrade document n. 97.09 / A. Montanari

German groups focusing on detector development and building

(long tradition in Aachen)

(slide 18 from Pierluigi`s talk)

general detector development plans

MTT hardware – dedicated technology

Idea: Scintillator based MTT readout by SiliconPhotoMultipliers

  • maintenance free

  • no gas needed

  • very fast

  • any requested resolution possible

  • no HV needed (Usupply < 100 V)

  • less power needed (< 0.2 mW/mm2)

  • very good timing (100 ps to 1 ns)

  • high photon detection efficiency (up to 65 %)

  • but high noise rate (up to 1 MHz/mm2 at 0.5 PE threshold) and small active surface (up to 3 mm x 3mm at the moment)

Best suited device for triggering at the moment:

- highest photon detection efficiency

- low noise

- will soon be produced in CMOS technology (cheap)

Hamamatsu SiPM:

100 µm x 100 µm pixels

Aachen IIIA / IIIB and DESY collaboration

Aachen IIIA / IIIB and DESY collaboration

  • Aachen IIIA: - simulations about light collection /SiPM signal timing - combining MTT with muon chamber

  • Aachen IIIB: - experience from tracker development - SiPM supply electronics development

  • Aachen IIIA + Aachen IIIB: (finally) building the MTT

  • DESY: HCAL group member, possible integration with HO

Aachen IIIA / IIIB and DESY collaboration

MTT at Aachen IIIA – Scintillator designs

Two possible designs:

“Traditional” one:

scintillator plates with embedded WaveLengthShifting fibers + light collecting in WLS fiber

→ more light/photon detector surface - mechanical effort

o good time resolution

“New” one:

SiPMs directly mounted to scintillator plates (was done with huge PMs)o low light yield - but readout perhaps possible (high pde, large SiPMs (~ price as smaller ones)

+ simple mechanical construction+ very good time resolution- maybe more readout channels, power consumption

WLS fiber

(green light)‏

scintillator (blue light)‏

photon detectors


Aachen IIIA / IIIB and DESY collaboration

MTT at Aachen IIIA – Light collection studies

diffuse reflection

- try to find best position of SiPMs, wrapping of scintillator, shape of WLS fiber

- have developed “standalone“ scintillator + SiPM simulation

- diploma student is working on GEANT simulation

“normal” reflection

total reflection

Aachen IIIA cosmics testing (student project)

Aachen IIIA / IIIB and DESY collaboration

MTT at Aachen IIIB

Aachen IIIB brings in experience from tracker (petals) assembling / testing:

- one focus: development of compact SiPM readout electronics- especially: development of a gain stabilization on a chip (SiPM gain is

temperature and maybe time and radiation dose


Aachen IIIB SiPM-cosmics testing

Aachen IIIA / IIIB and DESY collaboration

MTT at Aachen – common Aachen IIIA/B parts

  • timing (kind of coincidence, time resolution)

  • (trigger) electronics tests

  • build large test detectors

  • tests together with other detectors (muon chamber, petal)

SiPM mounted on Aachen pcb, first test with scintillator

tracker petal

CMS silicon petal

quality control

at Aachen IIlB

cosmic muon

MTT test detector

muon chamber

Aachen IIIA / IIIB and DESY collaboration


- DESY member of HCAL group (CASTOR)

- interested in combination MTT with HO

- change of HPD in SiPM for HO needed → exchange of initial two readout-boxes planned for this shut down → get experience with the longterm operation with SiPM (new detector technology, also at T2K starting 2009)

- further discussion between Muon and HCAL groups underway, need experiences with HO with SiPMs and for sure simulations everywhere

associated work

Associated work

associated work

Implementation of MTT into CMSSW

Scintillator very sensitive to background !

  • scintillator can probably not distinguish between kinds of particles

  • scintillator does not measure momenta

  • MIP produce less light than background (e.g. slow protons, electrons)

  • background rate of all (charged) particles including low momentum particles

  • timing of background (and signal)

  • momentum of background particles (absorbing / producing secondary particles)

associated work

Strategies to limit sensitivity of MTT to background

slow e-


  • Absorber (thin, between 2 scintillator layers):Absorbs low momentum particles between the two layers.→ MTT gets too thick ? Two layers too expensive ?

  • Use multiple scattering/magnetic field deflection

    → Does not work with one MTT element.

  • Set time-of-flight gate:Reduce sensitivity to neutron background, slow pions and kaons → Need high time resolution, more electronics ?

  • Set pulse height amplitude (=amount of light) limit:(background produces mostly more light than MIPs)

  • Combination with HO

MTT layer 1

absorber (Pb)

MTT layer 2



neutron induced proton

first steps

First steps

first steps

Simplest scintillator based detector

SiPMs directly coupled to front side of a piece of scintillator

+ very simple set up

+ thin construction

+ very good time resolution

- a lot of SiPMs needed

- many readout channels (but high resolution)

100 mm


idea: T.H. for SLHC

SiPMs (3 mm x 3 mm)

in unconventional position

first steps

Simulation results (2)

Assuming: - 90 % diffuse reflexion at surrounding 3M tape

- 3 mm x 3mm detectors - 65 % photon detection efficiency (80 % coupling efficiency)

4 PE threshold

first steps

Simulation results (2)

need 2 of 4 coincidence

(4 PET for each SiPM)

noise rate < 1 Hz

no correlation with SiPM position visible

efficiency > 80 % for 10 mm thick scintillators

(gets ~ 100 % for 95 % reflective wrapping)

position of SiPM

(to be tested with larger scintillators)

first steps

WLS fiber simulation



Simulation for WLS fiber setup (1)


(Hamamatsu 100 pixels,

1 mm x 1 mm)


WLS fiber (BCF-92)

piece of scintillator (BC-404)


simulated 10000 muons traverses


- uniform distributed, vertical particle transition

- require coincidence (interval < 10 ns) between both SiPMs with 3 PET

→ noise rate < 1 Hz

first steps

Simulation for WLS fiber setup (2)

light collection effect of WLS fiber huge

more than 98 % detection efficiency

(using 1 mm x 1 mm SiPMs)

time resolution of detector still good



  • MTT is a promising concept to include tracker data into L1 muon trigger: - DT and RPC can be kept as independent systems. - MTT can also solve DT occupancy problem (at L1-trigger).

  • Scintillator based MTT could be an easy and cheap solution:- It can be inserted in addition to existing detectors. - SiPMs are a very promising technology. - German groups can contribute to detector development and building. - MTT/HO: under discussion, several aspects to be clarified

  • At SLHC may need any kind of redundancy !