Title of Invention	"A PROCESS FOR PREPARATION OF RADIOPHOTOLUMINESCENT GLASS"
Abstract	According to present invention there is provided a process for the preparation of radiophoto1uminescent glass having a capacity to record incident gamma radiation thereby acting as a sensor of gamma radiation. The prepared glass is sensitive to only gamma radiation and it does not record neutron radiation. The radiophotoluminescent glass has a very high sensitivity and can record as low as 1 centi gray of incident gamma radiation and has the ability to record the incident gamma radiation from 1 to 1000 centi gray in a linear and uniform fashion. It has fast build-up time with ability to record 100% incident radiation within twenty-four hours and it does not suffer from the fading of the recorded information regarding the incident gamma radiation over a period of time. The prepared glass is uniform and is weather resistant with no loss of its characteristics over a period of time.

Title of Invention

"A PROCESS FOR PREPARATION OF RADIOPHOTOLUMINESCENT GLASS"

Abstract

According to present invention there is provided a process for the preparation of radiophoto1uminescent glass having a capacity to record incident gamma radiation thereby acting as a sensor of gamma radiation. The prepared glass is sensitive to only gamma radiation and it does not record neutron radiation. The radiophotoluminescent glass has a very high sensitivity and can record as low as 1 centi gray of incident gamma radiation and has the ability to record the incident gamma radiation from 1 to 1000 centi gray in a linear and uniform fashion. It has fast build-up time with ability to record 100% incident radiation within twenty-four hours and it does not suffer from the fading of the recorded information regarding the incident gamma radiation over a period of time. The prepared glass is uniform and is weather resistant with no loss of its characteristics over a period of time.

Full Text	FIELD OF INVENTION This invention relates to a process for the preparation of radiophotoluminescent glass for recording and measurement of gamma radiation. PRIOR ART Radiophotoluminescent glasses are utilised for recording and measurement of gamma radiations. These glasses work on the principle that the gamma radiation, incident on these glasses, cause structural changes in the glass leading to the formation of luminescent centers. When this glass block is excited with the ultraviolet light, it emits visible light, which in turn can be measured by a reading device comprising a photodiode. This visible light is a measure of gamma radiation absorbed by the radiophotoluminescent glass. These radiophotoluminescent glasses are known to the prior art. However, these glasses, known in the prior art, suffer from following disadvantages. Main disadvantage of the processes for the preparation of radiophotoluminescent glasses, known in the prior art, is that these processes result in radiophotoluminescent glasses that have a slow build up time and which require more than twenty-four hours to indicate even 90% of the total intensity of the gamma radiation exposed thereon. Another disadvantage of the processes for the preparation of radiophotoluminescent glasses, known in the prior art, is that these processes result in radiophotoluminescent glasses which suffer from fading with the result that the recorded information regarding the absorbed gamma radiation fades over a period of time. Yet another disadvantage of the processes for the preparation of radiophotoluminescent glasses, known in the prior art, is that these processes result in radiophotoluminescent glasses which do not provide linear response to the absorbed gamma radiation. Still another disadvantage of the processes for the preparation of radiophotoluminescent glasses, known in the prior art, is that these processes result in radiophotoluminescent glasses, which are also sensitive to incident neutrons and as such these glasses can not be exclusively utilised for measurement of gamma radiation. OBJECTS OF THE INVENTION Primary object of the invention is to provide a process for preparation of radio photoluminescent glass which is able to record and measure the gamma radiation, incident. upon it, thereby working as a sensor of incident gamma radiation. Another object of the invention is to provide a process for the preparation of radio photoluminescent glass, which does not record incident neutron radiation and thereby functions exclusively as a sensor for incident gamma radiation. Yet another object of the invention is to provide a process for the preparation of radio photoluminescent glass, which has a fast build-up time and which is capable of providing information about total 100% incident gamma radiation. Still another object of the invention is to provide a process for the preparation of radiophotolumlnescent glass, which has almost no fading and the recorded informtion regarding incident gamma radiation fades only by 5X over a period of six months. Yet further 'object of the invention is to provide a process for the preparation of radio photoluminescent glass, which has unit sensitivity and has one to one correspondence with the incident gamma radiation. Still further object of the invention is to provide a process for the preparation of radio photoluminescent glass, which is weather stable and which does not suffer from the loss of its characteristics over a period of time. Yet further object of the invention is to provide a process for the preparation of radio photoluminescent glass, which has high sensitivity and is able to record even as low as 1 centi gray of incident radiation. Still further object of the invention is to provide a process for the preparation of radio photoluminescent glass, which is capable of recording incident gamma radiation having intensity from 1 centi gray to 1000 centi gray. DESCRIPTION 0F THE INVENTION According to this invention there is provided a process tor preparation for radiophotoluminescent glass comprising the steps of : (i) Preparing a mixture by mixing aluminium phosphate, lithium carbonate and silver nitrate with ortho phospheric acid in a crucible (ii) drying of said mixture (iii) polymerising the mixture of glass matrix in calcination furnace by heating (iv) casting of glass matrix in a pre-heated sintered mould (v) annealing of glass (vi) polishing of the glass block (vii) cleaning of glass block In accordance with the present invention, the process for the preparation of radiophotoluminescent glass comprises of fol1 owing steps: ( i) Preparation of batch by mixing of almunium phosphate. 1ithium carbonate and si 1ver nitrate with ortho phospheric acid in an aluminium crucib1e 30-40X (weight wise) aluminum phosphate, 15-17% (weight wise) lithium carbonate and 3-4* (weight wise) silver nitrate are well mixed to form a powdered mix. This powdered mix is added to 54-56* (weight wise) ortho phospheric acid in an aluminum crucible under continuous stirring by a silica rod. The uniform agitation of the slurry helps in uniform distribution of the si 1ver. (ii) Drying of batch in oven at control 1ed temperature t The batch in the crucible is placed in an oven and the o temperature is raised at the rate of 100 C per hour up to 140 _+ o 10 C and then this temperature is maintained for 12-18 hours. During the drying process, the batch is stirred intermittently with silica rod to facilitate evaporation of water. ( i i i ) Pol ymerisat ion of g 1 ass ma tr.i x in ca i cinati on furnace by contro11ed heat ing After drying of the batch, the crucible with the batch is transferred to a calcination furnace already preheated at around o o 100-200 C preferably at 150 C. Then the temperature of the furnace is further increased in two stages. First, the o temperature is raised upto 260 C with the rate of increase in o temperature controlled at the rate of 10 C per hour. Next, the o o o temperture is raised from 260 C to 750 C at the rate of 45 + 5 C per hour. the batch is kept for four hours at this raised temperature for polymerisation of phosphate tetrahedra. ( i v ) Casting of g lass matr i x in a_ pre-heated s intered graphite mould The crucible with the glass matrix is transferred to a o electrically heated melting furnace kept at 750 C. The furnace is hearth type and the temperature of the furnace is raised at o the rate of 100 C per hour. The melt is stirred with silica rod o o intermittnetly between 1250 C to 1340 C for homogenisation o purpose. Next, the temperature is brought down to 1150 i 10 C at o the rate of 5 C per hour. After melting of the glass matrix, the crucible is taken out and the glass is poured on a pre-heated o (upto 200 C) sintered graphite mould of size 150 x 110 x 16 mm and is gently pressed with a graphite block of size 100 x 70 x 15 mm on the free surface of the glass.(v) Annealing of glass The complete block along with the glass is transferred to a muffle type annealing furnace kept at 400 °C. The glass is kept at 400 °C for 20 minutes and then is allowed to cool at the rate of 40-50 °C per hour up 300 °C. The furnace is then switched off and the glass is allowed to cool to room temperature with the natural cooling rate of the chamber. (vi) Polishing of the glass block The glass is cut to optimum size ( 15x 12 x 4 mm) and polished with a surface finish of X./4. (vii) Cleaning of glass block Finally, the polished glass block is washed with benzene, acetone, and water. The cleaned polished glass block is kept in clean tissue papers. The properties of the radiophotoluminescent glass, prepared in above manner, are as in the following. Density 2.6 gm/cm3 Transformation Temperature 430 °C Dilatometric Temperature 470 °C Durability 0.25% Refractive Index 1.51227 Abbe Number 66 The process of the present invention will now be illustrated with a working example, which is a typical example to illustrate the working of the invention and is not intended to be taken restrictively to imply any limitation on the scope of the invention. Working Example To prepare 100 gm of RPL Glass, 3.75 gm silver nitrate, 16.16 gm lithium carbonate and 31.36 gm aluminum phosphate are mixed and then added to 55.32 gm of ortho phospheric acid in an aluminum crucible. Mixture is then stirred continuously till a paste is formed. The mixture is then dried for 16 hours in an oven at about 140 ± 10 °C till evaporation of phosphorous pentaoxide stops. The dried mixture is then sintered in an electrically heated melting furnace at around 750 °C then raising the temperature at the rate of 100 °C per hour. The batch is then homogenised at 1300 °C and then the batch is transferred to a preheated graphite mould (up to 200 °C). The glass is then annealed byo transferring it to a muffle type annealing furnace kept at 400 C o o and then cooling it first upto 300 C at the rate of 40-50 C at and is subjected to controlled cooling. It is then cut into optimised size and polished optically upto ft/4 surface finish. The polished glass block is then cleaned with benzene, acetone, water and dehydrated alcohol. It is to be understood that the process of the present invention is susceptible to adaptations, changes and modifications by those killed in the art. Such adaptations, changes and modifications are intended to be within the scope of the present invention, which is further set forth with the fol1 owing claims. CLAIM A process for preparation of radiophotoiurninescent glass comprising the steps of: (i) Preparing a mixture by mixing aluminium phosphate, lithium carbonate and silver nitrate with ortho phospheric acid in a crucible (ii) drying of said mixture (iii) polymerising the mixture of glass matrix in calcination furnace by heating (iv) casting of glass matrix in a pre-heated sintered mould (v) annealing of glass (vi) polishing of the glass block (vii) cleaning of glass block 2. A process as claimed in claim 1 wherein mixture comprises said almunium phosphate about 30-40%, lithium carbonate about 15-17%, silver nitrate about 3-4% and ortho phospheric acid about 54-56% by weight. 3. A process as claimed in claim 1 wherein said mixture is prepared by mixing of said almunium phosphate, lithium carbonate and silver nitrate with said ortho phospheric acid in a crucible under continuous stirring. 4. A process as claimed in claim 1 wherein said drying is o done in an oven at temperature at 140 ± 10 C for 12-18 hours under intermittent stirring. 5. A process as claimed in Claim 1, wherein said polymerisation of glass matrix is done in a calcination furnace ' o at about 750 C for about four hours with the temperature being o o raised at the rate of 10 C per hour upto 260 C and then with the o c rate of 45 + 5 C per hour from 260 to about 750 C. 6. A process as claimed in claim 1, wherein said casting of the glass matrix is achieved by tranferring the said polymerised glass in an electrically heated melting furnace and o heating it up to a temperature of 1340 C with the rate of o increase in temperature being maintained at about 100 C per hour o and cooling it up to 1150 *. 5 C with the rate of cooling being o about 5 C per hour and then pouring it on pre-heated sintered graphi te moul d. 7. A process as claimed in claim 1, wherein said annealing is done by transferring said mould an a muffle type annealing o furnace at about 400 C and then cooling it first up to about o o 300 C with the cooling being maintained at the rate of 40-50 C per hour and then -cool irig-i-t up to room temerature with natural rate of cooling. 8. A process for preparation of radiophotol uminescent glass substantially as described and exemplified herein. 9. Rad iophoto 1 uminescent glass wherein prepared by a process as described substantially herein.

Full Text

FIELD OF INVENTION
This invention relates to a process for the preparation of radiophotoluminescent glass for recording and measurement of gamma radiation.
PRIOR ART
Radiophotoluminescent glasses are utilised for recording and measurement of gamma radiations. These glasses work on the principle that the gamma radiation, incident on these glasses, cause structural changes in the glass leading to the formation of luminescent centers. When this glass block is excited with the ultraviolet light, it emits visible light, which in turn can be measured by a reading device comprising a photodiode. This visible light is a measure of gamma radiation absorbed by the radiophotoluminescent glass. These radiophotoluminescent glasses are known to the prior art. However, these glasses, known in the prior art, suffer from following disadvantages.
Main disadvantage of the processes for the preparation of radiophotoluminescent glasses, known in the prior art, is that these processes result in radiophotoluminescent glasses that have a slow build up time and which require more than twenty-four hours to indicate even 90% of the total intensity of the gamma radiation exposed thereon.
Another disadvantage of the processes for the preparation of radiophotoluminescent glasses, known in the prior art, is that these processes result in radiophotoluminescent glasses which suffer from fading with the result that the recorded information regarding the absorbed gamma radiation fades over a period of time.
Yet another disadvantage of the processes for the preparation of radiophotoluminescent glasses, known in the prior art, is that these processes result in radiophotoluminescent glasses which do not provide linear response to the absorbed gamma radiation.
Still another disadvantage of the processes for the preparation of radiophotoluminescent glasses, known in the prior art, is that these processes result in radiophotoluminescent glasses, which are also sensitive to incident neutrons and as such these glasses can not be exclusively utilised for measurement of gamma radiation.
OBJECTS OF THE INVENTION
Primary object of the invention is to provide a process for preparation of radio photoluminescent glass which is able to record and measure the gamma

radiation, incident. upon it, thereby working as a sensor of incident gamma radiation.
Another object of the invention is to provide a process for the preparation of radio photoluminescent glass, which does not record incident neutron radiation and thereby functions exclusively as a sensor for incident gamma radiation.
Yet another object of the invention is to provide a process for the preparation of radio photoluminescent glass, which has a fast build-up time and which is capable of providing information about total 100% incident gamma radiation.
Still another object of the invention is to provide a process for the preparation of radiophotolumlnescent glass, which has almost no fading and the recorded informtion regarding incident gamma radiation fades only by 5X over a period of six months.
Yet further 'object of the invention is to provide a process for the preparation of radio photoluminescent glass, which has unit sensitivity and has one to one correspondence with the incident gamma radiation.
Still further object of the invention is to provide a process for the preparation of radio photoluminescent glass, which is weather stable and which does not suffer from the loss of its characteristics over a period of time.
Yet further object of the invention is to provide a process for the preparation of radio photoluminescent glass, which has high sensitivity and is able to record even as low as 1 centi gray of incident radiation.
Still further object of the invention is to provide a process for the preparation of radio photoluminescent glass,
which is capable of recording incident gamma radiation having intensity from 1 centi gray to 1000 centi gray.

DESCRIPTION 0F THE INVENTION
According to this invention there is provided a process tor preparation for radiophotoluminescent glass comprising the steps of :
(i) Preparing a mixture by mixing aluminium phosphate, lithium carbonate and silver nitrate with ortho phospheric acid in a crucible
(ii) drying of said mixture
(iii) polymerising the mixture of glass matrix in calcination furnace by heating
(iv) casting of glass matrix in a pre-heated sintered mould
(v) annealing of glass
(vi) polishing of the glass block
(vii) cleaning of glass block
In accordance with the present invention, the process for the preparation of radiophotoluminescent glass comprises of fol1 owing steps:
( i) Preparation of batch by mixing of almunium phosphate. 1ithium carbonate and si 1ver nitrate with ortho phospheric acid in an aluminium crucib1e
30-40X (weight wise) aluminum phosphate, 15-17% (weight
wise) lithium carbonate and 3-4* (weight wise) silver nitrate are
well mixed to form a powdered mix. This powdered mix is added to
54-56* (weight wise) ortho phospheric acid in an aluminum
crucible under continuous stirring by a silica rod. The uniform
agitation of the slurry helps in uniform distribution of the
si 1ver.
(ii) Drying of batch in oven at control 1ed temperature t
The batch in the crucible is placed in an oven and the
o temperature is raised at the rate of 100 C per hour up to 140 _+
o 10 C and then this temperature is maintained for 12-18 hours.
During the drying process, the batch is stirred intermittently with silica rod to facilitate evaporation of water.

( i i i ) Pol ymerisat ion of g 1 ass ma tr.i x in ca i cinati on furnace by contro11ed heat ing
After drying of the batch, the crucible with the batch is
transferred to a calcination furnace already preheated at around
o o
100-200 C preferably at 150 C. Then the temperature of the
furnace is further increased in two stages. First, the
o
temperature is raised upto 260 C with the rate of increase in
o
temperature controlled at the rate of 10 C per hour. Next, the
o o o
temperture is raised from 260 C to 750 C at the rate of 45 + 5 C
per hour. the batch is kept for four hours at this raised temperature for polymerisation of phosphate tetrahedra.
( i v ) Casting of g lass matr i x in a_ pre-heated s intered graphite mould
The crucible with the glass matrix is transferred to a
o electrically heated melting furnace kept at 750 C. The furnace
is hearth type and the temperature of the furnace is raised at
o the rate of 100 C per hour. The melt is stirred with silica rod
o o
intermittnetly between 1250 C to 1340 C for homogenisation
o purpose. Next, the temperature is brought down to 1150 i 10 C at
o the rate of 5 C per hour. After melting of the glass matrix, the
crucible is taken out and the glass is poured on a pre-heated
o (upto 200 C) sintered graphite mould of size 150 x 110 x 16 mm
and is gently pressed with a graphite block of size 100 x 70 x 15 mm on the free surface of the glass.(v) Annealing of glass
The complete block along with the glass is transferred to a muffle type annealing furnace kept at 400 °C. The glass is kept at 400 °C for 20 minutes and then is allowed to cool at the rate of 40-50 °C per hour up 300 °C. The furnace is then switched off and the glass is allowed to cool to room temperature with the natural cooling rate of the chamber.
(vi) Polishing of the glass block
The glass is cut to optimum size ( 15x 12 x 4 mm) and polished with a surface finish of X./4.
(vii) Cleaning of glass block
Finally, the polished glass block is washed with benzene, acetone, and water. The cleaned polished glass block is kept in clean tissue papers.
The properties of the radiophotoluminescent glass, prepared in above manner, are as in the following.
Density 2.6 gm/cm3
Transformation Temperature 430 °C
Dilatometric Temperature 470 °C
Durability 0.25%
Refractive Index 1.51227
Abbe Number 66
The process of the present invention will now be illustrated with a working example, which is a typical example to illustrate the working of the invention and is not intended to be taken restrictively to imply any limitation on the scope of the invention.
Working Example
To prepare 100 gm of RPL Glass, 3.75 gm silver nitrate, 16.16 gm lithium carbonate and 31.36 gm aluminum phosphate are mixed and then added to 55.32 gm of ortho phospheric acid in an aluminum crucible. Mixture is then stirred continuously till a paste is formed. The mixture is then dried for 16 hours in an oven at about 140 ± 10 °C till evaporation of phosphorous pentaoxide stops. The dried mixture is then sintered in an electrically heated melting furnace at around 750 °C then raising the temperature at the rate of 100 °C per hour. The batch is then homogenised at 1300 °C and then the batch is transferred to a preheated graphite mould (up to 200 °C). The glass is then annealed byo transferring it to a muffle type annealing furnace kept at 400 C
o o
and then cooling it first upto 300 C at the rate of 40-50 C at
and is subjected to controlled cooling. It is then cut into optimised size and polished optically upto ft/4 surface finish. The polished glass block is then cleaned with benzene, acetone, water and dehydrated alcohol.
It is to be understood that the process of the present invention is susceptible to adaptations, changes and modifications by those killed in the art. Such adaptations, changes and modifications are intended to be within the scope of the present invention, which is further set forth with the fol1 owing claims.

CLAIM
A process for preparation of radiophotoiurninescent glass comprising the steps of:
(i) Preparing a mixture by mixing aluminium phosphate, lithium carbonate and silver nitrate with ortho phospheric acid in a crucible
(ii) drying of said mixture
(iii) polymerising the mixture of glass matrix in calcination furnace by heating
(iv) casting of glass matrix in a pre-heated sintered mould
(v) annealing of glass
(vi) polishing of the glass block
(vii) cleaning of glass block
2. A process as claimed in claim 1 wherein mixture
comprises said almunium phosphate about 30-40%, lithium carbonate
about 15-17%, silver nitrate about 3-4% and ortho phospheric acid
about 54-56% by weight.
3. A process as claimed in claim 1 wherein said mixture is
prepared by mixing of said almunium phosphate, lithium carbonate
and silver nitrate with said ortho phospheric acid in a crucible
under continuous stirring.
4. A process as claimed in claim 1 wherein said drying is
o done in an oven at temperature at 140 ± 10 C for 12-18 hours
under intermittent stirring.
5. A process as claimed in Claim 1, wherein said
polymerisation of glass matrix is done in a calcination furnace ' o
at about 750 C for about four hours with the temperature being
o o
raised at the rate of 10 C per hour upto 260 C and then with the
o c
rate of 45 + 5 C per hour from 260 to about 750 C.

6. A process as claimed in claim 1, wherein said casting
of the glass matrix is achieved by tranferring the said
polymerised glass in an electrically heated melting furnace and
o heating it up to a temperature of 1340 C with the rate of
o increase in temperature being maintained at about 100 C per hour
o and cooling it up to 1150 *. 5 C with the rate of cooling being
o about 5 C per hour and then pouring it on pre-heated sintered
graphi te moul d.
7. A process as claimed in claim 1, wherein said annealing
is done by transferring said mould an a muffle type annealing
o furnace at about 400 C and then cooling it first up to about
o o
300 C with the cooling being maintained at the rate of 40-50 C
per hour and then -cool irig-i-t up to room temerature with natural rate of cooling.
8. A process for preparation of radiophotol uminescent
glass substantially as described and exemplified herein.
9. Rad iophoto 1 uminescent glass wherein prepared by a
process as described substantially herein.

Documents:

515-del-2001-abstract.pdf

515-del-2001-claims.pdf

515-del-2001-correspondence-others.pdf

515-del-2001-correspondence-po.pdf

515-del-2001-description (complete).pdf

515-del-2001-form-1.pdf

515-del-2001-form-18.pdf

515-del-2001-form-2.pdf

515-del-2001-form-3.pdf

515-del-2001-gpa.pdf

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Patent Number

219635

Indian Patent Application Number

515/DEL/2001

PG Journal Number

28/2008

Publication Date

11-Jul-2008

Grant Date

12-May-2008

Date of Filing

24-Apr-2001

Name of Patentee

ADDITIONAL DIRECTOR (IPR)

Applicant Address

Inventors:

#	Inventor's Name	Inventor's Address
1	ALLA RAMALINGA REDDY
2	RAMAN RAMACHANDRAN
3	JASBEER SINGH HOODA
4	PARITOSH KUNDU
5	PRADEEP KUMAR BHATNAGAR
6	ANUP CHAUDHURI
7	BASUDEB KARMAKAR

PCT International Classification Number

C03C 3/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA