Speaker
Dr
Fco. Rogelio Palomo Pinto
(Dpt. of Electronic Engineering, School of Engineering, Sevilla, Spain)
Description
F.R.Palomo[1], I. Vila[2], E.Curras[2], D.Moya[2], A.L.Virto[2], J.García-López[3], M.C.Jiménez[3]
[1] Corresponding author: rogelio@gte.esi.us.es.
Dpt. of Electronic Engineering, School of Engineering, Sevilla, Spain.
[2] Instituto de Física de Cantabria, IFCA, Santander, Spain.
[3] CNA, National Center of Accelerators, CSIC-University of Sevilla, Sevilla,Spain.
We present results of temperature measurements on a proton beam using Fiber Bragg Gratings as sensors. A Fiber Bragg Grating is a local periodic modulation of the refraction index in an optical fiber. The use of temperature measurements for beam profiling is a well-established technique, by means of thermocouples, [1], [2]. An FBG sensor is less intrusive due to its materials (SiO2, plastics) and their thickness (~125 m without coating), electrically passive and immune to EMI. They are as precise as thermocouples (<0.1 K) and extremely linear.
Under the proton beam, the FBG sensors transform the ionization interaction into wavelength shifts. The read out of the FBG sensor is made with a tunable laser beam shining through the optical fiber. The equivalence is 1 K for 10 pm of wavelength shift in case of heating. FBG sensors are extremely radiation resistant, far beyond 15 MGy, [3], without significative damage (radiation induces an additional wavelength shift that eventually saturates, [4].). Besides, the radiation induced wavelength shift can be avoided by using Type II FBG sensors, [5].
For our proof of concept test, a curtain of FBG sensors is exposed to a 13.3 MeV, 100 nA proton beam during several minutes in air, for a total of five irradiation periods. The accumulated wavelength shifts in two FBG exposed to the proton beam show . The on and off proton beam events are clearly visible in the FBG sensors curves, for a total of 5 peaks (on instants, 16.75, 16.97, 17.08, 17.28 and 17.88 h. There is also a temperature reference (331) off beam for calibration purposes.
References:
[1] A thermocouple-based beam profile monitor for an 800 MeV proton accelerator, P.D.Ferguson, W.F.Sommer, G.E.Mueller, M.J.Borden, Nuclear Instruments and Methods in Physics Research A, 344 (1994), pp. 300-306.
[2] Beam and target monitor using thermocouples Sato, T ,15th Meeting of the International Collaboration on Advanced Neutron Sources, v.1, Tsukuba, Japan, 6 - 9 Nov 2000, pp.308-313.
[3] Influence of the Fiber Coating on the Proton Radiation Sensitivity of Fiber Bragg Gratings, E.Curras, A.L.Virto, D.Moya, I.Vila, J.G.Carrión, M.Frövel, J.García-López, M.C.Jiménez, Y.Morilla and F.R.Palomo, Proceedings of RADECS 2011, Sevilla, September 19th-23rd ,2011.
[4] Fiber Bragg Gratings as high dose radiation sensors?, K.Krebber, H.Henschel and U.Weinand, Measurement Science and Technology, 17 (2006), pp.1095-1102.
[5] Radiation sensitivity of Bragg gratings written with femtosecond IR lasers, D.Grobnic, H.Henschel, S.K.Hoeffgen, J.Kuhnhenn, S.J.Mihailov and U.Weinan, Proceedings of SPIE, vol. 7316, 73160C-1-9.
Author
Dr
Fco. Rogelio Palomo Pinto
(Dpt. of Electronic Engineering, School of Engineering, Sevilla, Spain)
