beam test of low index sillica aerogel
DESCRIPTION
Beam test of low index sillica aerogel. Yukiyoshi Kon RCNP, Osaka University. Collaboration meeting @ Tiwan 2008/5/2. Low reflective index silica aerogel was developed by Chiba University group. To use as AC veto Counter, we tested this sillica aerogel by beam at LEPS . 2008/4/21,22 - PowerPoint PPT PresentationTRANSCRIPT
Beam test of low index sillica aerogel
Yukiyoshi KonRCNP, Osaka University
Collaboration meeting @Tiwan2008/5/2
Low reflective index silica aerogel was developed by Chiba University group.
To use as AC veto Counter, we tested this sillica aerogel by beam at LEPS .– 2008/4/21,22– Tabata, Saito, Kawai, Chiba University, Kon
Detection efficiency and mean # of photoelectron was estimated about index n = 1.015, 1.0082 and 1.0027.
Method to estimate efficiency• Aerogel Counter:
– Cerenkov effect
– PhotomultiplierEmission of photoelectrons from cathode obey
Poisson statistics.
• Detection efficiency:
n
n
1
,1cos
eNe
e NN
NNNP exp
!),(
ee NNP exp1),0(1
S1 S2C
S1, S2: Scintillation countersC: Cerenkov Counter
Cerenkov counter(: C)’s signal is taken with S1, S2 coincidence trigger.
Beam is injected inside Cerenkov counter perfectly.
Pulse hight distribution obteined by ADC outputs forms Poisson distribution.
all
pedee
all
pedee
N
NN
N
NN
log
1exp1
I. Adachi et al./Nucl. Instr. and Meth. in Phys. Res. A 355 (1995) 390-398
Counter design
Light guide box: width 125 x hight 260 x thickness 65Covered by reflector Alminized mylar & Gore-tex sheet. 4 Photomultiplier: Fine mesh type (Hamamatsu
Photonics H6614-70)Aerogel was arranged by hangging in midair by strings.
Beam test
Beam: Converting LEP into e+e- shower by 10mm x 10mm lead sheet.
Trigger: Tag x !UP x (S1 x S2 x S3) S1, S2: front Scintillation Counters, S3: backward Scintillation Counter.
Set up
LEP
S1
S2
S3C
TOF Wall
Convertor
Index and Reflectorn = 1.015 n = 1.0082 n = 1.027
40 mmMylar
Mylar Mylar Mylar (Plane)Gore-tex
65 mmMylar
Mylar Gore-tex
Mylar (empty box)
Gore-tex (empty box)
100 mm
100 mm
20 mmScillica aerogeln = 1.0027 was first beam test in the world.But, Transmission was bad.
n = 1.015 n = 1.0082 n = 1.0027
π 0.802 GeV/c 1.088 GeV/c 1.898 GeV/c
e 0.00293 GeV/c 0.00695 GeV/c 0.00397 GeV/c
Threshold momentums
Cerenkov angle
• Cerenkov angle:
• Beam: electron
• In very low index point, Cerenkov angle is a few degrees.
n: smaller
β
θ [rad.]
n = 1.0027, 1.0082, 1.015, etc.
n 1cos 1
1
Aerogel arangement
e
40 mm 65 mm
20 mm
100 mm
Light‘s pass length is shorter.But emitted photon is less.
Emitted photon is larger than 40mm one.But path length is longer.
Version A:
e
40 mm
Cerenkov light mainly is ejected to forward direction. It is difficult to go out from aerogel in horizontal dirrection.
Version B:Only n = 1.0027, mylar
Index dependence
n=1.015 n=1.0082 n=1.0027Analyzed event #: 10000 for all samples.
Mylar, 40mm
Pulse hight distribution was selected to get correct photoelectron event by TDC cut.4 photomultiplier‘s event # was summed up.
Photoelectron’s number became smaller, as soon as index was smaller.
n=1.015 n=1.0082 n=1.0027
Pedestal 9163
All 39984
Npe = 0.640Eff. = 0.771
Pedestal 13898
All 40000
Npe = 0.451Eff. = 0.653
Pedestal 25794
All 40000
Npe = 0.191Eff. = 0.355
Estimation - The number of mean photoelectron and efficiency
Pass length dependence40mm 65mm
Npe = 0.640Eff. = 0.771
Npe = 0.994Eff. = 0.899
Npe and efficiency was increased , as pass length longer.
Difference of aerogel arrangemnt
Npe = 0.191Eff. = 0.355
Npe = 0.168Eff. = 0.321
A B
Npe and efficiency of version B was little worse.
Difference of reflecting materials
Npe = 0.639Eff. = 0.771
Npe = 1.061Eff. = 0.913
Gore-texmylar
Efficiency ofGore-tex counter was better- it’s suitable for random reflection in light guide box.
Empty Counter
Npe = 0.014 Npe = 0.181
Gore-texMylar
Little Cerenkov light was emitted• Air Cerenkov ?
Photon # was more than mylar.• Scintillation light from Gore-tex ?
Summary
We tested low index sillica aerogel with beam, and estimated detection efficiency.
For NTPC Experiment, counter coverd Gore-tex one is not suitable for e+e- beto counter because of over veto the hadron.
AC beto counter was exchanged to (n=1.0082, version B, mylar) from (n=1.01, version B, Gore-tex).
Efficiency should be rechaecked another method, beacause pedestal couldn’t from distribution perfectly.
- Fitting with poisson distribution conboluted gaussian function.
n = 1.015 n = 1.0082 n = 1.027
40 mm0.771
0.653 0.355 0.3210.913
65 mm0.899
0.788 0.975
Efficiency