RD51Collaboration Meeting
08to11March2016
Dependenceontheincidenceangle
andpressure ofRelativeExtraction
Efficiency ofphotoelectrons froma
CsI photocathode
F.C.ROLO,F.I.G.M.BORGES,K. SA ITO,A .F.V.
CORTEZ,C.A .N.COND E
Laboratório deInstrumentação eFísica ExperimentaldePartículas (LIP-Coimbra)
PhysicsDepartment
UniversityofCoimbra
Coimbra,Portugal
E-mail:francisco.crolo@gmail.com
Introdution
RadiationDetectors
Photoelectric
Effect
Radiationinputtoelectricaloutput
Photocathodes
- quantum efficiency
#𝑒𝑚𝑖𝑡𝑒𝑑𝑒 (
#𝑝ℎ𝑜𝑡𝑜𝑛𝑠
Variationwithincidenceanglefor
variousatmospheres
§ Importantforoptimisingthe
performanceofdetectors
§ Fewdataavailableintheliterature
ExperimentalSetup
D2Lamp
Quartzwindow
Collimator
CollectionGrid
Photocathode stage
Linearmotion feedthrough
ExperimentalSetup
Limitations:
§ BroadSpectraldistributionofthelamp
§ Complexityofthevacuumsystem->poor
controlandknowledgeofthevacuumlevel
§ Evaporationofthephotocathode hastobe
doneoutsidethesystem
D2Lampspectraldistribution
ExperimentalSetup
Method
AnglevariationMeasurement:
1) Measurethephotocurrent for0°
2) Measurethephotocurrent
varyingtheangleby5°
3) Comparethosewith0° measures
E/pvariationMeasurement:
1) Measurethephotocurrent for
verylowreducedelectricfield
(E/p)
2) VaryE/pandtakesomevaluesfor
eachE/p
3) Comparethosewiththe
reference
Typical E/pMeasurement
Photocurrent
Photocurrent
TypicalAngleMeasurement
Time
Time
Fornow we mesured
RelativePhotocurrent
Xe- 1bar
Xe- 3bar
Xe- 2bar
35%
35%
35%
30%
30%
30%
25%
25%
25%
20%
20%
20%
15%
15%
15%
10%
10%
10%
5%
5%
5%
0%
0%
0
-5%
10
20
30
Angle(º)
40
50
60
0%
0
-5%
10
20
30
40
Angle(º)
(𝑽 / 𝑻𝒐𝒓𝒓 (𝟏 / 𝒄𝒎(𝟏 )
50
0
60
-5%
10
20
30
Angle(º)
40
50
60
Fornow we mesured
Xe - 1bar
Xe - 2bar
RelativePhotocurrent
(Reference:E/p=0)
Xe - 3bar
(Reference:E/p=0,005)
(Reference:E/p=0,005)
140
14
14
120
12
12
100
10
10
80
8
8
60
6
6
40
4
4
20
2
2
0
0
0
0,2
0,4
0,6
0,8
E/p(VTorr-1cm-1)
1
0
0
0,2
0,4
0,6
E/p(VTorr-1cm-1)
0,8
1
0
0,2
0,4
0,6
E/p (VTorr-1cm-1)
0,8
1
Inthe future
Inthenearfuturewewanttokeepthiskindofmeasurementsfor
someothergaseousatmospheresandlatermaybeadaptthesystem
sowecangetabsolutemeasurements.
Withthissetupwecanalsostudytheresponseofthephotocathode
withtheincidentangleforsomeotherparameters:
§ aging
§ humidity
§ substrate
§ heating
§ ...
Conclusions
§Thesystemgiveveryprecise
reproducibleresults.
§Measuments forXe at1,2and3bar
wereperformedshowingsimilar
behaviour.
§ThevariationofREEwithE/pisnot
angledependent.
AngleVariation
35,00%
Relativephotocurrent
§Anexperimentalsystemtomeasurethe
variationoftheRelativeExtraction
Efficiency(REE)inphotocathodeswith
thelightincidenceanglewasdeveloped.
30,00%
25,00%
20,00%
15,00%
10,00%
5,00%
0,00%
-5,00%
0
10
Average 1bar
20
30
40
50
Angle(º)
Average 2bar
Average 3bar
60
Thank you...