Post on 12-Jan-2016
RICH 2007 Dirk Wiedner / LHCb 1
The Usage of N-Perflourcarbons as RICH Radiators
RICH 2007 Dirk Wiedner / LHCb 2
The specifications
• Little chromatic dispersion• Refractive index sufficient O(1.001)• Good UV transmittance (CsI)• Long radiation length• Non flammable• Easy to use
N-perflourcarbons fulfill these specs
RICH 2007 Dirk Wiedner / LHCb 3
Refractive index
FROM: Gas Cherenkov detectors for high momentum charged particle identification in ALICEG. Volpe et. altera
n = 1.0021 @ 7eV
Gas (n-1)x104 @
CF4 5.3 180 nm
C4F10 15 180 nm
C5F12 21 180 nm
C6F14
Fluid!
2800 180nm
• Refractive index can be tuned by choosing the appropriate Perflourcarbon
• Very moderate chromatic dispersion, at 177 nm dn/dE [eV−1] = 53 × 10−6*
*Dissertation von Peter FaulandUniversit¨at Bielefeld
RICH 2007 Dirk Wiedner / LHCb 4
Transparency• Good transparency for clean CnFm
• Extinction in far UV ok for light gas as C3F8 – Photon detector should be sensitive above 180nm
100
1000
10000
110 120 130 140 150 160
Wavelength (nm)
C6F14
C5F12
C4F10C3F8
mol
ar e
xtin
ctio
n co
effi
cien
t,
(1/
cm/m
ol)
Chemical Physics Letters, volume 3, number 8, 1969, 649-651
RICH 2007 Dirk Wiedner / LHCb 5
Watch contaminations
• Benzene kills transparancy
1
10
100
1000
10000
150 175 200 225 250 275 300
Wavelength (nm)
Abs
orpt
ion
Coe
ffic
ient
(/c
m/b
ar)
.
0.1
1
10
100
1000
100 125 150 175 200
Wavelength (nm)
Abs
orpt
ion
(/cm
/bar
) .
Water
Oxygen
CO2
• Water and Oxygen should be kept low
150nm
200 nm
Water
RICH 2007 Dirk Wiedner / LHCb 6
Membrane cleaning• Membranes allow selection of kinetic diameter • CF4 and C4F10 can be well separated from Oxygen, Argon and
Nitrogen
0.01
0.1
1
10
100
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0
Kinetic diameter (A)
Sel
ectiv
ity r
elat
ive
to N
2 .
CO2
O2
ArN2
CF4 C4F10
UBE Industries, Specialty Chemicals and Products Division, High Purity Chemicals Business Unit, Ube Europe GmbH, Duseldorf, Germany.
RICH 2007 Dirk Wiedner / LHCb 7
C4F10 recovery
• C4F10 is a good Čerenkov radiator
• Widely used: Compass, Delphi, Hera-B, Hermes, LHCb
• Expensive gas: must be recovered before opening detector
• Example: LHCb Rich1
RICH 2007 Dirk Wiedner / LHCb 8
LHCb RICH1 C4F10 recovery
• Twofold membrane filters– Eliminates light gases– Exit can be used for recovery or direct recycling
• Fridge – Separates C4F10 from Argon, Nitrogen etc.
– Outputs liquid C4F10 to container
RICH 2007 Dirk Wiedner / LHCb 9
The test setup
RICH 2007 Dirk Wiedner / LHCb 10
The test setup
RICH 2007 Dirk Wiedner / LHCb 11
The test setup
RICH 2007 Dirk Wiedner / LHCb 12
The test setup
N2Out
RICH 2007 Dirk Wiedner / LHCb 13
The test setup
RICH 2007 Dirk Wiedner / LHCb 14
The test setup
RICH 2007 Dirk Wiedner / LHCb 15
0.01
0.1
1
10
100
1000
10000
-150 -100 -50 0 50 100
Temperature (oC)
Vap
or p
ress
ure
(hPa
)C4F10 C5F12 C6F14 C3F8
Vapor pressure of CnFm
RICH 2007 Dirk Wiedner / LHCb 16
Tests
• 20 recovery test with C4F10
• 13 runs with evaporation in source bottle
• 7 runs with external evaporation
RICH 2007 Dirk Wiedner / LHCb 17
Obstacles
• Mixture of different CnFm, O(5%) non C4F10
• Ice built up in compressor electronic box
• Up to 6.6 kg can stay in recovery rack
• Corrosion of 63 l bottles in lab– Liquid extraction line in bottle not gas tight
• C4F10 condensates at 1.2 bar overpressure
– Compression must go along with heating
• Liquid loss at >200l/h waste gas flow
RICH 2007 Dirk Wiedner / LHCb 18
Summary of recovery tests
• System works stable
• Efficiency in first 5 tests 81.5% av.
• Efficiency in next 15 tests 90.4% av.
• External evaporator works reliably
• 24 h for 4 m3 of LHCb RICH1 @ max. flow
• Next steps– Installation of recovery system– commissioning
RICH 2007 Dirk Wiedner / LHCb 19
Backup Slides