bad honnef 2006 cms - vdc 1 a drift velocity measurement chamber for cms (vdc) bad honnef 2006 cms -...

Bad Honnef 2006 CMS - VDC

1

A drift velocity measurement chamber for CMS (VDC)

Bad Honnef 2006 CMS - VDC title page

Jens [email protected]

~ 150 mm


2

Bad Honnef 2006 CMS - VDC structure

Structure● the CMS detector and its gas system

● necessity for a VelocityDriftChamber (VDC)

● the VDC setup

● the trigger (a chance for testing photodiodes)

● further improvements

● results

● HV curves

● classification of the results

● outlook


3

The CMS-detector and its gassystem

5 wheels

- 1 O2 analyser parallel

to each VDC

- 1 VDC / wheel (+ 1 backup chamber)

- 50 L/h per muon chamber

gasroom

CMS-detector

Endcap


4

Necessity ● E-field in muon chamber cell is inhomogeneous

● accuracy of muon chamber is limited by:- precision of drift time measurement- mechanical precision- knowledge of E- and B-field- drift velocity vd should be known better than 10 ‰

(so that error is smaller than other value's errors)

use a dedicated, small drift chamberwith homogeneous E-field to measure v

d

necessity


5

The VelocityDriftChamberchamber layout

cathode:U

c up to -15 kV,

E= 210 V/mm

5 MBq 90Sr sources

anode wire:U

a~ +1.8 kV

grounded ( U=0)

field shaping tubes

insulator (Araldite)

gas inlet

cathode holders (6) Al plates

shielding

power connection and filter for cathode

trig

ger

syst

em

E-field

V=1 Lsize ≈ milk bag (tetra pack©)

collimators(2 mm x 15 mm)

development:

diploma thesis

Georg Altenhöfer

drifting electrons

electron tracks

time difference --> drift velocity v

d

reference volume


6

Principle of operation

co

drift timefor

42 mm

photomultipliers

scintillator

source Sr90

collimator (Al wall)

field shaping electrodes

anode wiresensitive regionslit

cathode

collimator (Al wall)

me

chamber layout


7

features VDC has very homogeneous E-field

distance from anode /mm

x co

mpo

nent

of

elec

tric

fie

ld

/ V

/mm

electron beams= sensitive region (42 mm)

Garfield ver. 7.07

< 3 ‰tubes

16 5810 20 30 40 50 60 70

166.1

166.3

167.1

166.8

chamber layout


8

The trigger system● 2 kinds of "traditional" trigger systems

have been tested- 2 scintillators (2 mm and 10 mm thickness) with 1 photomultiplier (d=50 mm) per scintillator- 1 scintillator (10 mm) with 2 photomultipliers

● in preparation: one scintillator (4 mm

thickness) readout via 4 geiger-mode photodiodes (1 mm2)

chamber layout

- higher rate (from 33 Hz to 60 Hz)(less absorber, same scintillator)

new technology, high potential

- no HV needed (only ~60 V)

- fast (signal rise time < 2 ns)

- high quantum efficiency (over 40 % at 630 nm, cooled and 10 % at 400 nm, at room temperature )- but high noise rate ( ~2 MHz at 20˚C)

1 Hz random 4-foldcoincidencesexpected

scintillator


9

Further HV improvements

improvements

edges of chamber have been improved- no problems at the moment (until -16 kV)

add safety margin- longer holders (through backside) - add insulator to the backside of the cathode- enlarging the chamber by 10 mm


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present results

● accuracy of 0.4 ‰ for 5 min meas.(only statistical error !)

● no after pulses

● trigger rate improved

● optimal anode voltage set

● understanding of former peak height difference(unequal distances to PMs)

results

rate = 60 Hzσ(peak1) = (16.52±0.11) nsσ(peak2) = (17.36±0.16) nscounts(peak1) = 10151 counts(peak2) = 6633 signal to noise = 112

measurement with the prototype VDC

m


11

HV curves for anode (1)

HV-curves

constant difference

higher anode voltage → larger gas avalanche

Ua= 1.60 kV U

a= 1.85 kV

Ua= 2.60 kV

HV too low: too few signals HV optimal: sharp peaks, low sigma HV too high: too much background

(only statistical errors shown)

measurements:- duration: 10 min- U

c= 14 kV

coun

ts

sigm

a(pe

ak 1

) /

ns

(20.3±0.6) ns

(27.9±0.3) ns

(16.7±0.1) ns

Ua / kV

400 1300 time / 32/25 ns

25 400 250

working region

1.0

0.50.0

v d/ns1.0

0.5

0.01.6 2.6 U

a / kV

error for vd

independent from Ua


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HV curves for anode (2)field around anode accelerates

HV-curves

but time differences between electron beams are constant (around optimal voltage)anode voltage / kV anode voltage / kV

time

/

ns

anode voltage / kV

v d /

µm

/ns

not understood:effect outside working region

working region

t1

t2

∆vd = 0.07 µm/ns

time

/

ns


13

HV curves for cathode

HV-curves

kV

at Uc=15 kV: same E-field as max. in muon chambers

possible effects of overcurring

sigma of peaks decreases with E-field

gaussiandrift diffusionof electronsdNN

=1

4 Dtexp− x2

4Dt dxD Ar=4mm2 /s , x=20mmresp.60mm

=2D t

sigm

a(pe

ak1)

/

ns

v d /

µm

/ns

cathode voltage / kVbut ...

dominated by width of electron beam

data from peak width

measured

from vd

other effect in the gas

cathode voltage / kV

0.015

0.010

v d/ m /ns

vd

vd


14

Classification of the results

results

VDC:- unclean gas ? --> 99.7 % clean --> 80 ppm H

2O

(manufacturer)

- going to repeat measurement with 99.9995 % clean gas

measurement by T. Zhao, Y. Chen, S.Han, J.Hersch(1994)--> no information about systematic errors (E-field)--> cathode plates used

--> inhomogeneous E-field ? --> influence of dielectrica ?

preliminary data from VDC

Ar/CO2 85/15

comparison with other vd-measurement (only 1 serious with E-fields above 100 V/mm)


15

Estimation of errors

results

- homogenety of E-field: 3 ‰, but periodic, so estimate < 1.0 ‰

- power supply for cathode: accuracy: 5 V , amplitude max. 10 V, б ≈ 2 V observed < 0.2 ‰

- light propagation fluctuations in scintillator (simulation ) < 70 ps, ∆t= 1000 ns < 0.1 ‰

- TDC bin size 0.8 ns, measurement: = 0.16 ns, ∆t= 1000 ns

< 0.2 ‰ - statistical error (5 min measurement)

< 0.4 ‰

- multiple scattering -> Geant4 (soon). Error permitted, to stay below 10 ‰ total error < 8.0 ‰

2⋅

time

to d

etec

tor

/ n

s

vd/vd

0.29

0.25


16

Outlook

outlook

... if there is enough gas

➔ start of batch fabrication (7 chambers) start of batch fabrication (7 chambers)

➔ finalize trigger testfinalize trigger test

➔ simulation of the VDC with GEANT 4 (multiple scattering) simulation of the VDC with GEANT 4 (multiple scattering)

➔ determination of absolute systematic error (by using determination of absolute systematic error (by using more than one chamber) more than one chamber)

➔ integrating new electronics (VME coincidences, integrating new electronics (VME coincidences, discriminators, counters) discriminators, counters)

➔ transport to CERN: summer (06 ?) 2007transport to CERN: summer (06 ?) 2007

➔ start of CMS gas system: 0x/2007, start of CMS gas system: 0x/2007, start of LHC: 09/2007 (?) start of LHC: 09/2007 (?)

We will keep on testing ...


17

Peoples and references references

- master of the project: Hans Reithler- chief of the institute: Thomas Hebbeker- development, construction and first test of VDC: Georg Altenhöfer - building of VDC: Josef Grooten- planning, drawing of chamber-layout: Barthel Phillipps- electronics: Franz Adamczyk

&Günther Hilgers

&Henry Szczesny

- supporter for improving read-out-software: Michael Sowa- supporter for HV supply programming: Oleg Tsigenov

& Michael Bontenackels- final DAQ and DCS software: Gyorgy Bencze

&Anita Kapusi

& Gyula Zilisi- systematic tests and trigger development: J.F.

The VDC on the web: http://www.physik.rwth-aachen.de/~frangenheim/vdc.htmlThis talk: http://www.physik.rwth-aachen.de/~frangenheim/talks/BadHonnef2006.odsDiploma thesis of Georg Altenhöfer: http://www.physik.rwth-aachen.de/~altenhPaper about measurements of drift velocities:T. Zhao, Y. Chen, S.Han, J.Hersch; Nuclear Instruments and Methods in Physics Research A349(1994) 485-490

Geiger mode photodiodes from Photonique SA: http://photonique.ch/for further question: [email protected]

Debrećen


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Backup slides

backup slides


19

The CMS gas system

CMS detector


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Electronicchamber-layout

scintillator(BC-416)

light guide (plexiglass)

photomultipliers

(EMI, d=50 mm)

preamplifier + shaper(from UA1-experiment)

anode wire

discriminator

coincidence

18-channel NIM to ECL-Twisted Pair

converter (Desy F56)

timing unit (for gated mode)

3. Physikalisches Institut RWTH

Aachen(Günther Hilgers)

me

VME-Bus(CAEN VME-MXl2)

Win-PC with National interface

( LabView 8.0 DAQ-Software)

CAEN SY-127

HV for anode

HV for cathode

CAEN A432(4 ch., + 6 kV, 200 A)

CAEN A426(2 ch., -20 kV, 200 A)

CAEN-bus controller(CAEN C139)

CAMAC-Bus Linux-PC with Camac ISA-controller(C++-software based on "surface" by Christian Autermann)

TDC(CAEN V767, 0.8 ns resolution)

power-supply for photomultipliers(CAEN N126, 1 ch. , +6 kV, 3 mA)

temp. sensor

O2-content

pressuretemperature

HV to cathode+field shaping tubes (incl. filter and voltage divider)

drifting electrons


21

data analysis

results

➢ LabView gets data from TDC: time from anode pulses after trigger signal

➢ other data (pressure, temperature) also recorded

➢ analysis software (C++, root) reads data files and puts TDC data into histograms

➢ finding global maximum (small averaging regions)

➢ searching for a second peakon the left/right of global max.

➢ for each peak: searching downto the left/right until a value < average x factor is reached

➢ fit gaussian to fit region (iteratively)

➢ bad data can be detected, if no clear peaks are found

time 32/25 ns

time 32/25 ns

coun

ts


22

Anode curves

5 (=83 Hz)

coun

ts

/ 1

000/

min

Ua / kV

1.6 2.6

HV-curves


23

photodiodes trigger structurephotodiodes

scintillator

peltier elements

coin

cide

nce

coin

cide

nce

coincidence

photodiodes

mounting box

holders for cooling

backside made of plastic(isolating to the chamber)

preamplifier + filteringinside the box

Very compact !


24

pressure

pressure

pressure sensor produced in Aachen


25

O2 content

O2

O2 content is measured at the exit of the chamber

for additional detection of contamination


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inside the chamberinside the chamber

field shaping tubes are laser welded


27

Peoples and references references

- master of the project: Dipl. -Phys. Dr. rer. nat. Hans Reithler- chief of the institute: Dipl. -Phys. Univ.-Prof. Dr. rer. nat. Thomas Hebbeker- development, construction and first test of VDC: Dipl. -Phys. Georg Altenhöfer - building of VDC: mechanical master craftsman Josef Grooten- planning, drawing of chamber-layout: chief of mechanic Dipl. -Ing. Barthel Phillipps

- electronics : Dipl. -Ing. electrical engineering Franz Adamczyk

& attending technician Günther Hilgers

& Dipl. -Ing. electrical engineering Henry Szczesny- supporter for improving read-out-software: Dipl. -Phys. Michael Sowa- supporter for HV supply programming: Dipl. -Phys. Oleg Tsigenov

& Dipl. -Phys. Michael Bontenackels- final DAQ and DCS software: Dipl. -Phys. Dr. Gyorgy Bencze

& Dipl. -Phys. Anita Kapusi

& Dipl. -Phys. Dr. Gyula Zilisi- systematic test and trigger development: J.F.

The VDC on the web: http://www.physik.rwth-aachen.de/~frangenheim/vdc.htmlThis talk: http://www.physik.rwth-aachen.de/~frangenheim/talks/BadHonnef2006.odsDiploma thesis of Georg Altenhöfer: http://www.physik.rwth-aachen.de/~altenhPaper about measurements of drift velocities:T. Zhao, Y. Chen, S.Han, J.Hersch; Nuclear Instruments and Methods in Physics Research A349(1994) 485-490

Geiger mode photodiodes from Photonique SA: http://photonique.ch/

for further question: [email protected]

Debrećen

bad honnef 2006 cms - vdc 1 a drift velocity measurement chamber for cms (vdc) bad honnef 2006 cms -...

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