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ORIGINAL ARTICLE
Year : 2015  |  Volume : 38  |  Issue : 4  |  Page : 127-129  

Bremsstrahlung photon dose measurement inside Indus-2 synchrotron radiation source ring area


1 Indus Operation and Accelerator Physics Design Division, RRCAT, Indore, Madhya Pradesh, India
2 Health Physics Unit, Health Physics Division, BARC, Mumbai, Maharashtra, India

Date of Web Publication11-Feb-2016

Correspondence Address:
Saleem Khan
Indus Operation and Accelerator Physics Design Division, R.No-27, Indus-2 Building RRCAT, Indore, Madhya Pradesh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0972-0464.176162

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  Abstract 

In the synchrotron radiation source ring tunnel, various types of radiation such as bremsstrahlung photons, photo-neutrons, electrons and positrons are present due to the interaction of high energy electrons with structural material as well as gas molecules in a vacuum chamber and also due to cascade production. In this study, an attempt was made to quantify the bremsstrahlung photon dose inside the ring tunnel using direct reading dosimeters and thermoluminescent dosimeters.

Keywords: 60Co, bremsstrahlung radiation, calibration, direct reading dosimeter, Indus-2, thermoluminscent dosimeter


How to cite this article:
Khan S, Sahu T K, Kumar V, Haridas G. Bremsstrahlung photon dose measurement inside Indus-2 synchrotron radiation source ring area. Radiat Prot Environ 2015;38:127-9

How to cite this URL:
Khan S, Sahu T K, Kumar V, Haridas G. Bremsstrahlung photon dose measurement inside Indus-2 synchrotron radiation source ring area. Radiat Prot Environ [serial online] 2015 [cited 2022 Jan 19];38:127-9. Available from: https://www.rpe.org.in/text.asp?2015/38/4/127/176162


  Introduction Top


Indus-2 is a 2.5 GeV storage ring used for the production of synchrotron radiation (SR) and regularly operated at 100–150 mA. The injection energy is 550 MeV.[1] The radiation environment within the tunnel consists of bremsstrahlung and photo-neutrons. During the circulation of high energy electron in the ring, bremsstrahlung X-rays of high energy is generated due to the interaction of electrons with accelerator structure and residual gas molecules in the vacuum chamber.[2],[3] The bremsstrahlung photon energy spectrum depends on various factors such as incident electron energy, target material and target thickness and the spectrum ranges up to the incident electron energy.[4] In the case of Indus-2 (2.5 GeV storage ring) the bremsstrahlung spectrum ranges from few MeV to 2.5 GeV.[5] The bremsstrahlung photons produce photo-neutrons due to photon-neutron reactions. The storage ring consists of sixteen bending dipole (DP) magnets with bending angle 22.5 degree each and eight long straight sections of length 4.6 m each comprising of quadrupoles and sextupoles.[1] The schematic layout of Indus-2 is shown in [Figure 1]. For equipment as well as personnel safety, quantification of radiation dose in the storage ring tunnel is required. In this study quantification of radiation dose due to bremsstrahlung photons using thermoluminescent dosimeter (TLD) CaSO4:Dy and ion chamber based direct reading dosimeters (DRDs) were carried out and the results are presented.
Figure 1: Layout of Indus-2 synchrotron radiation source facility at Raja Ramanna Centre for Advanced Technology

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  Materials and Methods Top


Calibration of CaSO4:Dy TL discs

For the calibration and measurement, those TL discs were selected which were showing the response within 10–15% of the dose. In this study, calibration factor for CaSO4:Dy TL discs with respect to 60 Co was generated. Exposure to the discs from 30 mGy to 180 mGy was given from the source and the TL was measured using TLD reader Model No. TL 1009L made by NUCLEONIX. The calibration curve is shown in [Figure 2]. The calibration was used to estimate the relative dose with respect to 60 Co energy as there is no standard source available at the energy range of photons up to 2.5 GeV encountered in Indus-2 ring tunnel.
Figure 2: Calibration of CaSO4:Dy TL discs with 60Co

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Measurement of dose inside Indus-2 synchrotron radiation source ring

Eleven DPs and two other locations at injection septum of Indus-2 were selected for the dose measurement. The CaSO4:Dy TL discs along with DRDs were kept at inner and outer side of injection septum as well as bending magnets locations such as DP-2, 4, 5, 6, 7, 8, 9, 10, 11, 12, and 13. This measurement was repeated 3 times. The first measurement was carried out for 19 days of Indus-2 operation (injection, ramping and storage modes of operation are included), subsequent measurements were done for 18 days and 10 days, respectively.


  Results and Discussion Top


The calibration factor for CaSO4:Dy TL discs was obtained as 2.83E + 05 counts/Gy. The average dose rates obtained from the three sets of measurement using TLDs and DRDs are presented in [Table 1]. From the table, it is observed that:
Table 1: Average radiation dose measured by CaSO4:Dy TL discs and DRDs

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  • The injection region recorded low dose rate (~0.02–0.03 Gy/day) in comparison with other locations. A low dose at injection septum obtained may be attributed to the following reasons - Though injection beam loss is expected to be high the observed dose rate at injection septum is less because of the lower injection time than the beam storage time. The injection time is ~30 min whereas stored beam lifetime at 100 mA is ~15 h. Furthermore, the beam energy at injection is 550 MeV whereas the stored beam is of 2.5 GeV
  • At the DP locations, the dose obtained from the TLD is in the range 0.05–0.72 Gy/day. Variation in dose obtained at DP locations may be attributed to beam losses happening at respective DP locations
  • The dose recorded by DRD is found to be 10–46 times lower than that obtained from TLD at all the locations. This discrepancy in the dose may be due to prevailing energy spectrum within the tunnel where the contribution of low energy photon may be significant due to multiple scattering of the primary bremsstrahlung photons from the tunnel walls and nearby structures. It was expected that the dose rate contribution from high energy photons is dominant due to the bremsstrahlung production from the interaction of 550 MeV–2.5 GeV electrons with structural materials or residual gas molecules within the vacuum chamber. However, further studies are needed to establish the same.


The following conclusions are made from this present study:

  • Maximum dose obtained is at bending magnet DP-13 in Indus-2 ring and dose rate obtained is 0.72 Gy/day from bare CaSO4:Dy TL discs. This indicates higher beam loss take place at this location
  • Dose per day at injection septum is low as compared with other locations
  • Comparison of DRD and TLD data suggests the dominance of photons that are not of high energy. This needs to be further studied.


Acknowledgment

The authors are thankful to Dr. P. D. Gupta, Director, RRCAT, Shri P. R. Hannurkar, Head, Indus Operation and Accelerator Physics Design Division, RRCAT for their encouragement for this work. The authors are also grateful to Indus operation staff for their support to obtain data inside Indus-2 SRS ring area.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

1.
Singh G, Hannurkar PR, Shukla SK, Thakurta AC, Prabhu SS, Puntambekar TA, et al. Status of Indus-2 Synchrotron Radiation Source. InPAC 2011.  Back to cited text no. 1
    
2.
Available from: http://www-pub.iaea.org/MTCD/publications/PDF/trs188_web.pdf. [Last accessed on 2014 Jan 10].  Back to cited text no. 2
    
3.
Available from: http://www.ncrponline.org/Publications/Press_Releases/144press.html. [Last accessed on 2014 Jan 10].  Back to cited text no. 3
    
4.
Haridas G, Vipin D, Nayak MK, Thakkar KK, Sarkar PK, Sharma DN. Determination of dose buildup thickness for absorbed dose measurement in high energy electron-photon radiation at electron storage rings. Radiation Protection Dosimetry 2006;121(2):92–8.  Back to cited text no. 4
    
5.
Sahani PK, Nayak MK, Haridas G, Bandyopadhyay T, Hannurkar PR. Evaluation of radiological conditions in the experimental hutch of SEXAFS Beamline of Indus-2 due to introduction of a Photon Beam Shutter. InPAC 2013.  Back to cited text no. 5
    


    Figures

  [Figure 1], [Figure 2]
 
 
    Tables

  [Table 1]



 

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