ichiro adachi for the aerogel rich r&d group kek rich2004 2004.dec.01 study of highly...

Ichiro Adachifor the aerogel RICH R&D group

KEK

RICH2004

2004.Dec.01

Study of Highly TransparentSilica Aerogel as RICH Radiator

Introduction Aerogel production New solvent and optimization Optical quality Design considerations Conclusions

5th International Workshop on RIng Imaging Cherenkov Counters(RICH2004) 2

Acknowledgements

Coating business promotion group,Matsushita Electric Works, Ltd.

http://www.mew.co.jp/e-aerogel/


Introduction

Proximity focusing RICH using silica aerogel as Cherenkov radiator (talked by Peter Krizan) PID device in the forward region at the Belle detector Silica aerogel with n=1.05 as baseline design

Requirements on aerogel radiator Transparent

• Excellent quality for downstream tileFor multiple radiator case

(talked by Samo Korpar) Hydrophobic Reasonable size Crack-free

Aerogel radiator

Photodetector

Readout electronics

Cherenkov photon

n=1.05


Aerogel production

Colloidal formation

Treatment for hydrophobic

Supercritical drying Use CO2 extraction Safer due to low supercritical point

• 31degree & 7.5MPa

nSi(OR)4 + 4nH2O nSi(OH)4 + 4nH2O hydrolysisnSi(OH)4 (SiO2)n + 2nH2O condensation

3-dimensional network

alcohol

cf: methanol: 240degree & 8.1MPa

ammonia


Aerogel production so far

Lots of experience in making aerogel tiles (1994-1997) For the Belle Aerogel Cherenkov counter ~7000 blocks of 10x10x2cm3 ranging n=1.010-1.030 Optimization done for them

Optical quality gets worse if index goes beyond ~1.04

Tra

nsm

issi

on le

ngt

h(m

m)

Refractive index

drop quickly when n>1.04Transmission length~12mm at n=1.05

at 400nm How to improve?


New production technique(1)

New solvent introduced:DMF(N,N-di-methly-formamide) Use DMF together with Methanol as solvent

Our trial with DMF Transmission length(400nm)

~40mm for n=1.050 obtained

chemical formula HCON(CH3)2

molecular weight 80.14

usageDissolve various organic c

ompounds

remarks

Low volatility

Stable in normal condition

Avoid breathing vapor

0

10

20

30

40

50

1.02 1.03 1.04 1.05 1.06 1.07 1.08refractive index

transmission length (mm)

Methanol solventDMF solvent


New production technique(2)

Why DMF effective ? Internal surface area for methanol and DMF samples were compared i

n nitrogen vapor adsorption method

0

100

200

300

400

500

600

700

800

900

1st measurement 2nd measurement

Methanol sample

DMF sample

nitr

og

en

su

rfa

ce a

dso

rptio

n(m

2/g

)

BET method from MEW

DMF is expected to help making up higher porosity, suggesting making smaller pores in a sol-gel process

DMF sample has larger internal surface area than methanol one

As a result, higher transparency


DMF mixing ratio(%)

21.49

25.6823.77

31.84

18.28

33.87

40.63

36.58

25.0023.18

16.61

22.5224.13

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

40.00

45.00

50.00

0 20 40 60 80 100

H2O 24mol

H2O 28mol

H2O 32mol

Optimization using DMF

H2O quantity

T.L

.(40

0nm

)

High transparency with DMF >~ 70%

Clear peak in H2O quantity

Optimization done by making small samples with 40x40x10mm3

MOH only DMF only

25.10

18.28

22.59

36.58

18.43

24.13

11.71

40.63

8.75

31.84

16.172

33.8731.64

22.52

13.33

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

40.00

45.00

50.00

10 15 20 25 30 35 40 45

DMF 100%

DMF 85%

DMF 75%

How about larger and thicker sample?


Large sample production

100x100mm2 with 10/15/20mm thickness Sets of optimized parameters(for n= 1.050) provided from small sampl

es.

produce samples of n= 1.045-1.060

100x100x20mm3 n=1.050

No cracks

Sample we have obtained


Optical quality- Transmission -

0

20

40

60

80

100

200 300 400 500 600 700 800

parameter set1parameter set2

wave length(nm)

Comparison in transmissions between 2 sets of parameters for 100x100x10mm3 samples

T = A exp( Ct/4) • C: clarity factor• A: surface factor

0

2

4

6

8

10

clarity factor(μm4/ )mm

Clarity factor

set2

set1

mean:0.000633(μm4/mm)

mean:0.000912(μm4/mm)

target n=1.050


Optical quality- Transmission length -

Transmission length at 400nm

For 13 out of 36 samples, T.L. exceeds 40mm

• A long tail to low T.L. region may suggest a possible instability in alcogel production• More investigation necessary

0

2

4

6

8

10

22.1 24.1 26.1 28.1 30.1 32.1 34.1 36.1 38.1 40.1 42.1 44.1 46.1

transmission length(mm)


Optical quality- Refractive index -

0

2

4

6

8

10

12

index

target 1.045

target index

measured index

1.045 1.0456 ±0.0003

1.050 1.0518 ±0.0003

1.055 1.0534 ±0.0004

1.060 1.0606 ±0.0005

target 1.050

target 1.055

target 1.060

Refractive index management

Fine tuning will be done

• measured with Fraunhofer method(405nm laser)• systematic error not included

(measured)


Crack-free sample

Making “crack-free” aerogel tiles is another issue

0 20 40 60 80 100

10mm

15mm

20mm

n=1.05 sample

thickness

# of crack-free/total # of samples(%)

For 10mm thick samples, 100 % crack-free, while 70% if thickness is 20mm

This yield may be improved by tuning mixing ratio at sol-gel process as well as supercritical drying conditions

100x100mm2 cross section


Hydrophobic feature

Hydrophobic feature tested Aerogel put into water and compare trans

mission between before & after this

0

10

20

30

40

50

60

70

80

90

100

0 100 200 300 400 500 600 700 800

Wavelength [nm]

Transmittance [%]

beforeafter

T.L.(400nm): 25.5mm 28.2mmbefore after

Even better! washing effect?

Hydrophobicity well possessed


Beam test results

To confirm aerogel quality, beam test has been performed

T.L.(400nm):40.9mmrefractive index:1.053thickness:18.75mm

2003 March beam test

Transmission length(mm)

Npe

2001 beam test

improvement


0

10

20

30

40

50

60

70

80

90

100

200 300 400 500 600 700 800

wave_length(nm)

transmission(%)

n=1.050&1.055

Further attempt for multiple-layer aerogel(1)

Multiple-layers in one aerogel tile 2 (or more) layers with different refractive indices Two layers attached directly at molecular level Easy to handle when considering a multiple radiator scheme Insensitive to possible surface effect

n=1.050

n=1.045

“combined” T.L.(400nm)=41.1mm


Further attempt for multiple-layer aerogel(2)

We will compare various quantities among the following test samples:

n=1.050

n=1.050

n=1.050

n=1.050

n=1.055

crack

transparency

index

boundaryn=1.050

n=1.045

n=1.055

Even triple layers in a single tile produced!

Investigating the best solution

Try more!!!

“aerogel-focusing”


Design considerationsas RICH radiator(1)

Flatness of aerogel block is important when one stacks or cover a certain area with aerogel tiles

Meniscus causes “gap” between radiators

Aerogel block

This was made by the fact that one surface of an alcogel always faces outside during aging process.

Produce alcogel in the sealed vessel (with a cover) and is left inside it during aging

3 layers (100x100x10mm3 size) stacked

Another merit: surface quality can be better

Gap found ~< 1.0mm



Aerogel tile in hexagonal shape is desirable due to smaller loss of Cherenkov photons at edges Cut into hexagonal shape from square block Machining device of “water-jet” thanks to hydrophobic nature

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Surface quality has to be checked in a test beamExcellent precision in angle and length

1cm thick of 1.050 sample


0

0.2

0.4

0.6

0.8

1

1.2

0 20 40 60 80

day

Araldite(gluing glue onsurface)

DP-190(luing glue onsurface)

Aron Alpha(gluing glueon surface)

Rapid Araldite(gluingglue on surface)


How to hold aerogel blocks can be a potential problem in mechanical design Adhesive can deteriorate aerogel optical quality If not, we can use a simple bonding in constructing a real detector

T(4

00nm

) ra

tio

No deterioration when DP-190 is used

DP-190


Conclusions

Aerogel for RICH radiator has been developed Production of aerogel tiles with n=1.05 has been succes

sfully done and transmission length at 400nm has reached 40mm Issues for a stable production and index management

Optical quality of our samples has been examined in a test beam and improvements confirmed

Further challenges are going on Thicker and bigger blocks Multiple-layer blocks Machining possibility …. etc

ichiro adachi for the aerogel rich r&d group kek rich2004 2004.dec.01 study of highly...

Documents

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aerogel tiles

dmf samples

ratio of dmf

belle detectorsilica

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