The production and use of a nuclear microprobe of ions at MeV energies

Radiation damage of mylar foils by a nuclear microprobe

“…However, for biological or medical samples [10][11][12][13][14][15], which can be simulated approximately by organic or plastic materials [31][32][33] such as mylar (Du Pont; stoichiometry= C10H804; density p = 1.39 g/cm3; melting temperature Tm=523 K; minimum thickness for homogeneous foils d= 1 gm), one has a much smaller heat conduction coefficient: k (mylar) = 0.0016 W/cmK at TO --293 K. For a typical sample thickness d = 10 gm and an energy loss dE/dx(mylar)= 15.7 keV/gm one finds P = 790 W/cm 2 leading to a significant temperature increase A T= 68 K. Such a sizeable temperature increase could have effects on organic or biological samples, which have been studied in some detail in recent years [1,[26][27][28][29][30]. Quantitative studies of the radiation damage in organic samples showed evidence [1,[22][23][24][25][26][27][28][29][30][34][35][36][37][38] that sputtering and lateral displacements (due to nuclear recoils) have a negligible influence on the chemical composition of the sample (less than 0.1%).…”

“…Quantitative studies of the radiation damage in organic samples showed evidence [1,[22][23][24][25][26][27][28][29][30][34][35][36][37][38] that sputtering and lateral displacements (due to nuclear recoils) have a negligible influence on the chemical composition of the sample (less than 0.1%). The electronic energy loss causes the above temperature increase of the sample and may result in bond-breaking of molecular chains, which in turn may lead to desorption of volatile atoms and molecules.…”

“…In good vacuum the heat transport by radiation or convection is negligible compared to conduction, thus [1] A T= Tma x-TO = (Pr]) (…”

“…Nuclear microprobes have been applied to elemental analysis in a broad range of fields, using various ion beams and analysis techniques ( [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] and references therein). However, in most of these applications the PIXE technique (Proton-Induced-X-ray-Emission) was used with the following typical beam parameters: proton energy E o--3 MeV, current I--0.5 hA, irradiated sample area A 0 = 10 ~m 2 (for a radius of r 1 = 1.8 gm), accumulated charge Q = 1 IxC; the corresponding current density is J= 3.1 x 1016 protons/cm 2 s and the fluence is ~ = 6.2 • 1019 protons/cm 2.…”

Irradiation Facilities of the Takasaki Advanced Radiation Research Institute

“…The beam current is usually in the range from 0.1 pA to 10 pA, in the case of a diameter of 2 µm on the image point. The history of microbeam technology began in the 1970s with the advent of proton microbeams, which were first used for local elemental analysis at mesoscopic length scales [24,25]. Research and development in microbeam technology and applications at TIARA have been ongoing since 1990.…”