MAVERIC: Exploring Space Visualization Technology Through Academic Flight Programs

Magnetic Vector and Remote Imaging Communication satellite (MAVERIC) is a science and technology CubeSate designed and built by students at the University of Southern California (USC) and Space Engineering Research Center (SERC). MAVERIC is a student-led and built CubeSat under the Department of Astronautical Project Class for Microsatellites, with a mission to test out science and technology

Thermoluminescence optically stimulated luminescence and ESR studies on LiAl(5)O(8):Tb

The LiAl(5)O(8):Tb phosphor has been prepared by solution combustion synthesis. LiAl(5)O(8):Tb shows two TL peaks at 160 and 330 degrees C respectively. Continuous Wave OSL (CW-OSL) of LiAl(5)O(8):Tb phosphor is recorded. ESR studies have been carried out to identify centres responsible for TL peaks observed in LiAl(4)O(8):Tb. Room temperature ESR spectra of irridiated LiAl(5)O(8):Tb phosphor exhibit two distinct centres. The first ESR line is assigned to a V-centre. The second ESR line is assigned to F(+) centre. Both the ESR line appear to correlate with 160 degrees C TL peak LiAl(5)O(8):Tb phosphor

Defect centres and thermoluminescence in CaSO4 : Dy, Ag phosphor

The defect centres formed in the TL phosphor CaSO4:Dy,Ag are studied using the technique of Electron Spin Resonance. The Ag co-doped phosphor exhibits three glow peaks around 130, 220 and 375 degrees C in contrast with the two glow peaks observed in the CaSO4:Dy phosphor at 130 and 220 degrees C at a gamma ray dose of 1Gy. ESR studies show that the additional peak at 375 degrees C correlates with a Ag2+ centre formed due to gamma irradiation and observable only below -170 degrees C. The Ag2+ centre is characterised by an axial g-tensor with principal values g(parallel to) = 2.38 and g(perpendicular to) = 2.41. ESR studies further indicate that the precursor to a centre observable at low temperature (-170 degrees C) appears to act as the recombination centre for the TL peak at 375 degrees C; this radical is characterised by the g-values g(parallel to) = 2.0023 and g(perpendicular to) = 2.0038 and is assigned to SO3- radical. It is observed that there is more incorporation of Ag in the CaSO4:Dy system as compared with that in pure CaSO4 system

TSL, OSL and ESR studies ZnAl2O4 : Tb phosphor

ZnAl2O4:Tb phosphor was prepared by combustion synthesis. ZnAl2O4:Tb exhibits three thermally stimulated luminescence (TSL) peaks around 150, 275 and 350 degrees C. ZnAl2O4:Tb exhibits optically stimulated luminescence (OSL) when stimulated with 470 nm light. Electron spin resonance (ESR) studies were carried out to identify defect centres responsible for TSL peaks observed in ZnAl2O4:Tb. Two defect centres are identified in irradiated ZnAl2O4:Tb phosphor and these centres are assigned to V and F+ centres. V centre appears to correlate with the 150 degrees C TSL peak, while F+ centre could not be associated with the observed TSL peaks. (C) 200

Electron spin resonance and thermoluminescence studies in CaSO4: Dy,Ag phosphor

The defect centres formed in the thermoluminescence (TL) phosphor CaSO4: Dy,Ag are studied using the technique of electron spin resonance (ESR). The Ag co-doped phosphor exhibits three glow peaks around 130 degrees C, 220 degrees C and 375 degrees C, in contrast to the two glow peaks observed in the CaSO4: Dy phosphor at 130 degrees C and 220 degrees C, at gamma ray dose of 1 Gy when the TL measurements were carried out in the spectral region 300-650 nm. ESR studies show that the additional peak at 375 degrees C correlates with a Ag2+ centre formed owing to gamma-irradiation and observable below -170 degrees C. The Ag2+ centre is characterized by an axial g-tensor with principal values g(parallel to) = 2.38 and g(perpendicular to) = 2.41. ESR studies further indicate that the precursor to a centre observable at low temperature (-170 degrees C) appears to act as the recombination centre for the TL peak at 375 degrees C; this radical is characterized by the g-values g(parallel to) = 2.0023 and g(perpendicular to) = 2.0038 and is assigned to the SO3- radical. It is observed that there is more incorporation of Ag in the CaSO4: Dy system as compared with that in the pure CaSO4 system. The variation of Ag2+ ESR intensity with Ag concentration as well as with dose in the range 0.3 - 120 kGy is studied. The Ag2+ ESR signal and TL saturate at 2 x 10(4) Gy, but the intensity of the SO3- radical continues to increase up to the studied dose of 1.2 x 10(5) Gy. The intensity of the SO3- radical decreases with Ag concentration in CaSO4: Dy,Ag, in agreement with the TL model proposed in this work

Role of defect centres in thermoluminescence mechanism of Tb(3+) doped MgAl(2)O(4)

Magnesium aluminated (MgAl(2)O(4)) doped with terbium was prepared by combustion synthesis. Defect centres of various techniques such as Electron Spin Resonance (ESR), Thermoluminescence (TL) and Optically Stimulated Luminescence (OSL). TL studies on MgAl(2)O(4):Tb(3+) show two TL peaks at 120 and 340 degrees C. (TL) and Optically Stimulated Luminescence (OSL). TL studies on MgAl(2)O(4):Tb(3+) MgAl(2)O(4): Tb(3+) exhibits OSL when stimulated with 470 nm blue light. ESR study shows two defect centres with g = 2.011 and g = 2.0052 which are assigned to V-centre and F(+) centre, respectively. Step annealing ESR technique study suggests that V-centre is correlated to 120 degrees C TL peak whereas F(+) centre is correlated with both the 120 and 340 degrees C TL peaks. A TL mechanism is proposed. ESR-OSL correlation studies are carried out. The results of ESR-OSL correlation study along with TL bleaching study support the proposed TL mechanism of 120 degrees C TL peak

Thermoluminescence, optically stimulated luminescence and ESR studies on LiAl₅O₈:Tb

426-428 The LiAl5O8:Tb phosphor has been prepared by solution combustion synthesis. LiAl5O8:Tb shows two TL peaks at 160 and 330°C, respectively. Continuous Wave OSL (CW-OSL) of LiAl5O8:Tb phosphor is recorded. ESR studies have been carried out to identify defect centres responsible for TL peaks observed in LiAl5O8:Tb. Room temperature ESR spectra of irradiated LiAl5O8:Tb phosphor exhibit two distinct centres. The first ESR line is assigned to a V-centre. The second ESR line is assigned to F+ centre. Both the ESR lines appear to correlate with the 160°C TL peak of LiAl5O8:Tb phosphor. </smarttagtype

ESR and TL mechanism in CaSO4 : Ag co-doped phosphors

Thermoluminescence (TL) studies have been carried out on CaSO4 : Mn, CaSO4 : Ag, Mn, CaSO4 : Ag, Nd, CaSO4 : Ag, Mn, Nd, CaSO4 : Ag, Zr and CaSO4 : Ag, Mn, Zr phosphors. It is found that TL at 360 degrees C in CaSO4 : Ag, Mn, Nd is about 40 times that of CaSO4 : Ag, Mn and about 170 times that of CaSO4 : Ag, Nd. This shows that the presence of an efficient luminescent centre (Mn2+) as well as a trivalent impurity (such as Nd3+ or Y3+) is important for enhancement of TL at 360 degrees C in the CaSO4 : Ag, Mn, Nd phosphor system. Electron spin resonance (ESR) studies show that the peak at 360 degrees C correlates with an Ag2+ centre formed due to gamma-irradiation and observable only below -170 degrees C. The Ag2+ centre is characterized by an axial g-tensor with principal values g(parallel to) = 2.38 and g(perpendicular to) = 2.41. ESR studies further indicate that the precursor to a centre observable at low temperature (-170 degrees C) appears to act as the recombination centre for the TL peak at 360 degrees C. The low temperature centre is characterized by the g-values g(vertical bar vertical bar) = 2.0023 and g(perpendicular to) = 2.0038 and is assigned to the SO3- radical

Energy response study of thermoluminescent dosimeters to synchrotron radiation in the energy range 10-35 keV

172-174 LiF:Mg,Ti, LiF:Mg,Cu,P and CaSO4:Dy TLDs are worldwide used in the field of medical dosimetry, personnel monitoring and environmental monitoring. In view of the wide spread applications of synchrotron radiation for material research and diagnostic radiology in particular medical imaging, the present study of the energy response of some popular TLDs was undertaken. For the energy response study the most useful energy range 10-35 keV of synchrotron radiation was chosen and the present experimental work was carried out at SYRMEP beam line of Elettra Synchrotron Accelerator facility, Bassoviza, Trieste, Italy. The LiF based TLDs in the form of chips and disc, and CaSO4:Dy in the form of disc of thicknesses 0.8 mm and 0.4 mm made up of mixture of CaSO4:Dy phosphor and Teflon in the weight ratio 1:3 were used. The energy of the synchrotron radiation was calibrated using a Si (111) double crystal monochromator and several thin foils starting from Zn with Kedge 9.659 keV to KI compound with Kedge 33.169 keV. The energy response of the TLDs were normalized with respect its response to 60Co and corresponding relative response was evaluated. It was found that for CaSO4:Dy discs the relative response is about 12 at 25 keV which is maximum and subsequently falls down on either side of energy for both 0.4 mm and 0.8 mm thick discs. The relative response at 10 keV was found to be about 4.5 and 6 for 0.8 mm and 0.4 mm thick discs of CaSO4:Dy respectively. Maximum relative response of LiF:Mg,Cu,P chip of thickness 0.4 mm was found to be about 1.26 at 25 keV and it also exhibited lower response on either side of energy. LiF:Mg,Ti chips and discs show maximum response at the 30 keV which were 1.33 and 1.39, respectively. At 10 keV which was the lowest energy used in the present study, the relative response was always found to be less than 1 for LiF based TLDs. The relative response of the TLDs evaluated in the present experiment was compared with the published value in the literature and also confirmed through theoretical calculation using ratio of mass absorption coefficient of these materials with respect to air. </smarttagtype