P.S.Flower RAL PPD, CMS Meeting CERN, 1st. Feb 2000. The selection of an adhesive for bonding the VPTs to the PbWO 4 crystals in the end cap electromagnetic

P.S.Flower RAL PPD, CMS Meeting CERN, 1st. Feb 2000.

The selection of an adhesive for bonding the

VPT’s to the PbWO4 crystals in the end cap

electromagnetic calorimeters

P.S.Flower RAL


Contents Dow Corning RTV 3145

• Adhesive Requirements

• Refractive index

• Transmission

• Radiation damage

• Gluing

• Drying of glue

• Handling

• Unbonding

• Conclusion


Requirements

• Refractive index between 1.5 and 2.18

• Transmits UV• Does not darken

under radiation• Does not

embrittle under radiation

• Bonds well

• Does not impose stresses on crystal

• Stable for life of experiment

• Does not form bubbles

• Dries quickly• Easy to use • Can be

unbonded


The effect of μ of adhesive

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 5 10 15 20 25 30 35 40 45 50 55

PWO to Glass 1.3

PWO to Glass 1.6

PWO to Glass 2.0

PWO to Glass 1.82

PWO to Glass 1.45

PWO to Glass 1.9

PWO to Glass 1.55

Transmission PWO - Resin - Glass, as a function of incident angle for resin ref index 1.3, 1.6, 2.0,1.82. 1.45 glass 1.52, PWO 2.18, no account taken of bi-refringence

Tra

nsm

issi

on

Incident angle (Degrees)

0.80.810.820.830.840.850.860.870.880.890.9

0.910.920.930.940.950.960.970.980.99

0 5 10 15 20 25 30 35 40 45

PWO to Glass 1.3

PWO to Glass 1.6

PWO to Glass 2.0

PWO to Glass 1.82

PWO to Glass 1.45

PWO to Glass 1.9

PWO to Glass 1.7

PWO to Glass 1.55

Transmission PWO - Resin - Glass, as a function of incident angle for resin ref index 1.3, 1.6, 2.0,1.82. 1.45 glass 1.52, PWO 2.18, no account taken of bi-refringence

Tra

nsm

issi

on

Incident angle (Degrees)


Refractive index of RTV

• a = 12.79 b = 115.38c = -11.92d = -74.69

1.4

1.5

1.6

1.7

1.8

1.9

300 350 400 450 500 550 600 650 700

CERN RTV dataSellmeier fitPWO EmissionPhilips UV glassSchott BK7Fused SilicaSchott Duran

Refractive index of RTV (Montecchi) and fit to Sellmeier dispersion equation

Refr

acti

ve i

nd

ex

Wavelength (nm)

22

2

22

2

1d

c

b

a

windowVPTAdhesivePbWO4


Sample preparationGuide blocks

Pressure block

Windows

Spacers

Adhesive

• 1 mm quartz or glass plates • Clean Ethyl alcohol

Distilled water 2.5 % solution Decon 90 Distilled water Distilled water

• Adhesive 157 μ 898 μ 1586 μ


Calculation of transmission

• Use different thicknesses of adhesive

• Eliminate refractive index and glass absorption terms

I1I0

I2 I3

R1 R2

1

1

2

3

4

R3 R4

I5I4 I6 I7I0

x1 x2 x3

2

1

1

nn

nnR

AxII 100

7

710

2'2

2

1

I

ILog

xxA

2x'2x


Sample measurement

• Collimate beam• Sample must be perpendicular to

beam• accurately positioned ±10 μ• Reproducibly positioned

• λ 20 Dual beam spectrophotometer


Results

0102030405060708090

100

250 300 350 400 450 500 550 600 650 700

T45, 157 micron Dow

T46, 898 micron Dow

T47, 1586 micron Dow

T10, 954 micron glass

Wavelength (nm)

Ext

erna

l tra

nsm

issi

on (%

)

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

300 350 400 450 500 550 600 650 700

T45-T46 cm-1

T46-T47 cm-1

T45-T47 cm-1

Abs

orpt

ion

coef

ficie

nt (c

m-1

)

Wavelength (nm )


Absorption of DOW RTV3145

• Comparison of results with published data, M.Montecchi

0.01

0.1

1

10

300 350 400 450 500 550 600 650 700

RTV absorption RAL

RTV CERN

Ab

so

rpti

on

le

ng

th (

cm

-1)

Wavelength (nm)

RTV3145


γ Irradiation of samples• Brunel

15 Gy/h

• 1.7 Ci 60Co

Light tight box

Sample

Microscope slide glass

Plate glass

Support platform 60Co Sources

7 cm

7 cm

• P Bonner MRC3.16 kGy/h

• 2 off 2000Ci 60Co


γ Irradiation, results

• 205 kGy in 64 hours, adhesive 1155 μ thick

Radiation damage for T53, 205 kGy

0

20

40

60

80

100

200 400 600 800 1000

Wavelength (nm)

% o

f lig

ht

tra

ns

mit

ted

After irradiation

Before irradiation

Radiation damage for T56 (thick dow)

0

20

40

60

80

100

200 400 600 800 1000

Wavelength (nm)

% o

f li

gh

t tr

an

sm

itte

d

Before exposure

After exposure

• 205 kGy in 64 hours, adhesive 66 μ thick


Gluing procedure

• Fill syringe with RTV Dow 3145

• Centrifuge for 1 min at app. 3800 rpm, (2000 g)

• Dispense resin. Settings Gas 80 psi, Grey, taper tip nozzle, time 1.35 sec

• Press VPT on to crystal, allow meniscus to form.

• Hold in position for 2 hours

• EFD 1500XL Dispenser


Tests on resins

• 5 samples DOW RTV 3145, high viscosity

• Resin thickness 0.119 ± 0.010 mm

• Skew mean 3.9 m rad.

• One part resin, constant viscosity, long usable time

22 mm discs on 26 mm squares, cleaned 0.9mm microscope slides

• 4 samples DOW Sylgard, low viscosity

• Resin thickness 0.023 ± 0.003 mm

• Skew mean 0.7 m rad.

• Two part resin, variable viscosity, short usable time


Curing, Manufacturers Spec.

• Manufacturers spec

• Skin over time 50 min (25)

• Tack free time 1.5 hrs

• Cure, 0.5 mm 24 hours

• Cure 3.2 mm 72 hours

• Full cure 3.2 mm 7 days

• Cures by neutral alkoxy reaction with moisture in the air.

• Releases methanol on curing

• 98% Non volatile

• 50 % humidity at 23 ºC taken as normal

• At less than 30% humidity, curing slowed


Curing measurements

• Student, C Pattison, noticed adhesive in syringe picked up colour from rubber plunger

• This colour disappeared when adhesive dried


Drying testsCuring of glue

0

2

4

6

8

10

12

14

0 24 48 72 96 120 144 168 192 216 240Hours

mm

of d

ried

glu

e

100 micron thick glue

500 micron thick glue

• Initially all thicknesses dry at same speed

• Curing is moisture diffusion process

• After 48 hours, when the glue has dried about 4 mm; 100 micron glue dries at about 1 mm/day500 micron glue dries at about 1.4 mm/day


Handling Tests on Dow Corning RTV 3145

• After 5 min no slip observed

• After 30 min 100 g supported

• After 35 min 200 g supported

• After 40 min 225 g broke free

weight

32 mm dia glass bottle

Glass plate


Unbonding

• Literature suggests acidulated dichloromethane dissolves RTV3145.

• Nitromorse paint stripper contains dichloromethane.

• Unstuck bottle, 24 hours after gluing with 20 hours soaking in nitromorse.

• RAL “resin rotter” is dichloromethane, phenol and formic acid.


ConclusionDow Corning RTV3145

• Refractive index• UV Transmission• Radiation darkening• Radiation

embrittlement • Adhesive bonding• Stresses on crystal• Long term stability• Bubbles• Drying• Ease of use • Can be unbonded

• OK• OK• OK

• OK• OK• OK• Not tested• OK• OK• OK• Not yet

solved

Documents

P.S.Flower RAL PPD, CMS Meeting CERN, 1st. Feb 2000. The selection of an adhesive for bonding the VPTs to the PbWO 4 crystals in the end cap electromagnetic