24 th International Conference on Nuclear Tracks in

24 th International Conference on Nuclear Tracks in Solids 1 - 5 September 2008, Bologna Track Core Size of Proton and Heavy Ions in PADC Detectors Tomoya Yamauchi Kobe University, Japan Bologna, 2008 24 th Int. Conf. Nuclear Tracks in Solid

24 th International Conference on Nuclear Tracks in Solids 1 - 5 September 2008, Bologna Organization Tomoya YAMAUCHI, Yutaka MORI, Keiji ODA, Kobe University, Graduate School of Maritime Sciences, 5 -1 -1 Fukaeminami-machi, Kobe, Japan. Nakahiro YASUDA, National Institute of Radiological Science, 4 -9 -5 Anagawa, Inage-ku, Chiba, Japan. Rémi BARILLON, Institut Pluridisciplinaire Hubert Curien, 23 rue du Loess, Strasbourg, France. アンスティチュート・プリュリィディシプリネール・ユベール・キュイア Bologna, 2008 24 th Int. Conf. Nuclear Tracks in Solid

24 th International Conference on Nuclear Tracks in Solids 1 - 5 September 2008, Bologna Outline of the present study • Motivation & Purpose • Tracks in PADC • • UV-method: UV-visible absorption spectra, Track overlapping model (core size) • AFM-Method: Surface observation by Atomic Force Microscope after short-time etching (core size) • IR-method: Fourier transform-IR absorption spectra, G value (chemical Summary modification) Bologna, 2008 24 th Int. Conf. Nuclear Tracks in Solid

24 th International Conference on Nuclear Tracks in Solids 1 - 5 September 2008, Bologna Motivation & Purpose • For the development of new SSNTDs: with higher sensitivity: 5 ke. V/µm >>> 0. 5 ke. V/µm, with controllable detection thresholds. • To elucidate the track structure and track formation process in PADC and other polymers Bologna, 2008 24 th Int. Conf. Nuclear Tracks in Solid

24 th International Conference on Nuclear Tracks in Solids 1 - 5 September 2008, Bologna Materials • PADC: poly(allyl diglycol carbonate) BRYOTRAK (Fukuvi Chemical Industry) / CR-39 • PC: Bisphenol A polycarbonate Macrofol KG (Good fellow) Bologna, 2008 24 th Int. Conf. Nuclear Tracks in Solid

24 th International Conference on Nuclear Tracks in Solids 1 - 5 September 2008, Bologna What is track core? In some physical models, track core is treated as the region where the primary or direct ionization is dominant, surrounded by the track halo or penumbra, that is produced by the secondary electrons or delta-rays. In this work, …… Bologna, 2008 24 th Int. Conf. Nuclear Tracks in Solid

24 th International Conference on Nuclear Tracks in Solids 1 - 5 September 2008, Bologna What is track core? Track core size by three different ways: 1) UV-method: UV-method optically modified region due to the creation of some types of damage 2) AFM-method: AFM-method region where the local etching rate is significantly enhanced 3) IR-method: IR-method region where carbonate ester bonds and ether bonds are lost Bologna, 2008 24 th Int. Conf. Nuclear Tracks in Solid

24 th International Conference on Nuclear Tracks in Solids 1 - 5 September 2008, Bologna UV-method UV-Visible absorption spectra of PADC Fig. 1 UV-Visible spectra of a PADC sheet and the monomer. C=O carbonyl Fig. 2 UV-Visible-Near IR spectra of a PADC sheet. 2751 nm: 3635 cm-1 : H 2 O anti-symmetric 2820 nm: 3550 cm-1 : OH, H 2 O symmetric 2880 nm: 3470 cm-1 : C=O the first overtone Bologna, 2008 24 th Int. Conf. Nuclear Tracks in Solid

24 th International Conference on Nuclear Tracks in Solids 1 - 5 September 2008, Bologna UV-method Irradiations were carried out using a tandem Van de Graaff accelerator at Graduate School of Maritime Sciences, Kobe University. Table 1. Irradiation condition. Ion species Incident energy H+ 3. 4 Me. V KUMS He 2+ 5. 1 Me. V KUMS C 4+ 8. 5 Me. V KUMS O 4+ 7. 0 Me. V KUMS Bologna, 2008 24 th Int. Conf. Nuclear Tracks in Solid

24 th International Conference on Nuclear Tracks in Solids 1 - 5 September 2008, Bologna UV-method UV-Visible spectra of PADC sheets exposed to energetic protons in vacuum 1 st 2 nd 1 st 2 nd Fig. 3 UV-Visible spectra of PADC sheets exposed to 3. 4 Me. V proton beams. Fig. 4 UV-Visible spectra of PADC sheets exposed to 3. 4 Me. V proton beams at higher fluences. The first peak is at 240 nm and the second one is at 280 nm. Bologna, 2008 24 th Int. Conf. Nuclear Tracks in Solid

24 th International Conference on Nuclear Tracks in Solids 1 - 5 September 2008, Bologna UV-method Dependence of the peak height and peak height ratio on proton fluence: 280 nm/240 nm Fig. 5 Changes in the absorbance at the first and the second peaks with proton fluence. Fig. 6 Changes in the peak height ratio with proton fluence. The height of 1 st peak decreased around 2. 5 x 1013 ions/cm 2. 2. The proportionality was lost at 1. 0 x 1013 ions/cm. Bologna, 2008 24 th Int. Conf. Nuclear Tracks in Solid

24 th International Conference on Nuclear Tracks in Solids 1 - 5 September 2008, Bologna UV-method Track overlapping and UV absorption spectra Fig. 7 Without track overlapping, the optical density should be simply doubled when the fluence is doubled. Tracks are assumed to be simple cylinders. Bologna, 2008 24 th Int. Conf. Nuclear Tracks in Solid

24 th International Conference on Nuclear Tracks in Solids 1 - 5 September 2008, Bologna UV-method Track piling (random number): track radius = 3. 5 nm 100 nm Fig. 8 Evolution of track piling with fluence (simulation). Bologna, 2008 24 th Int. Conf. Nuclear Tracks in Solid

24 th International Conference on Nuclear Tracks in Solids 1 - 5 September 2008, Bologna UV-method Pileup of tracks (model) Les feuilles mortes Drops of rain Fig. 9 Evolution of track overlapping at various track radii. Bologna, 2008 24 th Int. Conf. Nuclear Tracks in Solid

24 th International Conference on Nuclear Tracks in Solids 1 - 5 September 2008, Bologna UV-method Critical fluence where the overlapping becomes significant Fig. 10 Evolution of track overlapping with fluence. Fig. 11 Relation between the critical fluence and track radius. Bologna, 2008 24 th Int. Conf. Nuclear Tracks in Solid

24 th International Conference on Nuclear Tracks in Solids 1 - 5 September 2008, Bologna UV-method Track core radius versus stopping power Fig. 12 Relation between the track core radii and stopping power from the UV method. NIM B 208 (2003)149 -154. Bologna, 2008 24 th Int. Conf. Nuclear Tracks in Solid

24 th International Conference on Nuclear Tracks in Solids 1 - 5 September 2008, Bologna UV-method HIMAC for heavier ions Heavy Ion Medical Accelerator in Chiba Table 2. Ion species Incident energy O 8. 6 Me. V HIMAC Ne 18. 8 Me. V HIMAC Si 27. 0 Me. V HIMAC Ar 35. 0 Me. V HIMAC Fe 80. 0 Me. V HIMAC Port Bologna, Plaza Chiba 2008 24 th Int. HIMAC共同利用研究成果発表会 Conf. Nuclear Tracks in Solid

24 th International Conference on Nuclear Tracks in Solids 1 - 5 September 2008, Bologna UV-method Track core radius versus stopping power Fig. 13 Relation between the track core radii and stopping power from the UV method (HIMAC). NIM B 236 (2005)318 -322. Bologna, 2008 24 th Int. Conf. Nuclear Tracks in Solid

24 th International Conference on Nuclear Tracks in Solids 1 - 5 September 2008, Bologna UV-method Track core radius by UV-method Fig. 14 Relation between the track core radii and stopping power from the UV method. Bologna, 2008 24 th Int. Conf. Nuclear Tracks in Solid

24 th International Conference on Nuclear Tracks in Solids 1 - 5 September 2008, Bologna AFM-method Track core radius of fission fragments by AFM Fig. 16 Evolution of minute etch pit of fission fragments in the subsurface layer. The intersection on the coordinate indicates the core radius of fission fragments of about 6 nm. Fig. 15 Typical AFM images of etched PADC. The samples were etched in 6 M KOH solution at 70 ºC for 2 min (a) and 50 s (b). RM 37 (2003)119 -125. Bologna, 2008 24 th Int. Conf. Nuclear Tracks in Solid

24 th International Conference on Nuclear Tracks in Solids 1 - 5 September 2008, Bologna HIMAC and VIVITRON (Strasbourg) Table 3. AFM-method Ion species Incident energy O 8. 6 Me. V HIMAC Ne 18. 8 Me. V HIMAC Si 27. 0 Me. V HIMAC Ar 35. 0 Me. V HIMAC Fe 80. 0 Me. V HIMAC I Xe 200. 0 VIVITRON Me. V 240. 0 HIMAC Me. V Bologna, 2008 24 th Int. Conf. Nuclear Tracks in Solid 250. 0

24 th International Conference on Nuclear Tracks in Solids 1 - 5 September 2008, Bologna AFM-method Track core radius by AFM-method Fig. 17 Etch pits of Fe ion. Etching time: 60 s. Fig. 18 Evolution of minute etch pit of heavy ions. Bologna, 2008 24 th Int. Conf. Nuclear Tracks in Solid

24 th International Conference on Nuclear Tracks in Solids 1 - 5 September 2008, Bologna AFM-method Track core radius versus stopping power Fig. 19 Relation between the track core radii and stopping power from the AFM and UV methods. Track core radii from the AFM method are greater than those from the UV methods for relatively heavier ions. Rev FMS. KU 2 (2006)179 -184. Bologna, 2008 24 th Int. Conf. Nuclear Tracks in Solid

24 th International Conference on Nuclear Tracks in Solids 1 - 5 September 2008, Bologna IR-method FT-IR spectra of PADC Fig. 20 FT-IR spectra of PADC films with various thickness. Fig. 21 Changes in absorbance for some bands of PADC with film thickness. Beer-Lambert law Bologna, 2008 24 th Int. Conf. Nuclear Tracks in Solid

24 th International Conference on Nuclear Tracks in Solids 1 - 5 September 2008, Bologna IR-method Loss of carbonyl along tracks in PADC Fig. 22 Spectral change of PADC in IR region by Fe ion irradiation. Fig. 23 Decrease of carbonate ester bonds with heavy ion fluence. Bologna, 2008 24 th Int. Conf. Nuclear Tracks in Solid

24 th International Conference on Nuclear Tracks in Solids 1 - 5 September 2008, Bologna IR-method Track core radius by IR-method Fig. 24 Relation between the track core radii and stopping power from the IR-method (GANIL&HIMAC). RM 40 (2005)224 -228. RM 43 (2008)S 106 S 110. Fig. 25 Relation between the track core radii and stopping power from the IR-method (HIMAC). JJAP 47 (2008)3606 -3609. Bologna, 2008 24 th Int. Conf. Nuclear Tracks in Solid

24 th International Conference on Nuclear Tracks in Solids 1 - 5 September 2008, Bologna discussion Track core radius by UV, AFM and IR methods Fig. 26 Relation between the track core radii and stopping power from the three methods. Bologna, 2008 24 th Int. Conf. Nuclear Tracks in Solid

24 th International Conference on Nuclear Tracks in Solids 1 - 5 September 2008, Bologna discussion Track core radius by UV, AFM and IR methods Fig. 27 Relation between the track core radii and stopping power from the three methods. Bologna, 2008 24 th Int. Conf. Nuclear Tracks in Solid

24 th International Conference on Nuclear Tracks in Solids 1 - 5 September 2008, Bologna discussion Track core radius and G value (1/3) Experimentally obtained relation: Where F is fluence. At a fluence of 1 ion/cm 2, This indicates the number of decreased bond per unit length of one track, i. e. damage density, L: Bologna, 2008 24 th Int. Conf. Nuclear Tracks in Solid

24 th International Conference on Nuclear Tracks in Solids 1 - 5 September 2008, Bologna discussion Track core radius and G value (2/3) G value is attained by dividing L by the average stopping power in films, . If the track core radius is proportional to the square root of stopping power, G value was independent of the stopping power, as: Bologna, 2008 24 th Int. Conf. Nuclear Tracks in Solid

24 th International Conference on Nuclear Tracks in Solids 1 - 5 September 2008, Bologna discussion Track core radius and G value (3/3) Fig. 28 Relation between the track core radii and stopping power. Fig. 29 Relation between G value and stopping power. Bologna, 2008 24 th Int. Conf. Nuclear Tracks in Solid

24 th International Conference on Nuclear Tracks in Solids 1 - 5 September 2008, Bologna discussion Tracks in PADC by UV method Fig. 30 Relation between the track core radii and stopping power in PADC. Bologna, 2008 24 th Int. Conf. Nuclear Tracks in Solid

24 th International Conference on Nuclear Tracks in Solids 1 - 5 September 2008, Bologna discussion Tracks in PADC Fig. 30 Relation between the track core radii and stopping power in PADC. Fig. 31 Relation between the G value for loss of C=O and stopping power in PADC (1). Bologna, 2008 24 th Int. Conf. Nuclear Tracks in Solid

24 th International Conference on Nuclear Tracks in Solids 1 - 5 September 2008, Bologna discussion Tracks in PADC Fig. 30 Relation between the track core radii and stopping power in PADC. Fig. 32 Relation between the G value for loss of C=O and stopping power in PADC (2). G value = 17 (/100 e. V) for gamma-ray !! Bologna, 2008 24 th Int. Conf. Nuclear Tracks in Solid

24 th International Conference on Nuclear Tracks in Solids 1 - 5 September 2008, Bologna Summary 1/2 Higher G values at lower stopping power in PADC not in PC Bologna, 2008 24 th Int. Conf. Nuclear Tracks in Solid

24 th International Conference on Nuclear Tracks in Solids 1 - 5 September 2008, Bologna Summary 2/2 Good selections of the molecule structure between two carbonate ester bonds can provide us sufficient polymers for SSNTDs. Bologna, 2008 24 th Int. Conf. Nuclear Tracks in Solid

24 th International Conference on Nuclear Tracks in Solids 1 - 5 September 2008, Bologna Thank you for your attention! Grazie! Bologna, 2008 24 th Int. Conf. Nuclear Tracks in Solid

24 th International Conference on Nuclear Tracks in Solids 1 - 5 September 2008, Bologna G value: ICRU report 60, 1998 Fundamental Quantities and Units for Ionizing Radiation • The radiation chemical yield, G(x), of an entity, x, is the quotient of n(x) by , where n(x) is the mean amount of substance of that entity produced, destroyed, or changed in a system by the energy imparted, , to the matter of that system, thus, Unit: mol J-1 The related quantity, called G value, has been defined as the number of entities produced, destroyed or changed by an energy imparted of 100 e. V. The unit in which the G value is expressed is (100 e. V)-1. A G value of 1 (100 e. V)-1 corresponds to a radiation chemical yield of 0. 104 µmol J-1. ICRU: International Commission on Radiation Units and Measurements Bologna, 2008 24 th Int. Conf. Nuclear Tracks in Solid

24 th International Conference on Nuclear Tracks in Solids 1 - 5 September 2008, Bologna Occupied area by tracks: A(n) at fluence of n (ions/cm 2), track area of s Probability A(n-1) fall into the occupied area 1 -A(n-1) fall into the non-occupied area Fig. 10 Fraction of the occupied area by tracks. Bologna, 2008 24 th Int. Conf. Nuclear Tracks in Solid

24 th International Conference on Nuclear Tracks in Solids 1 - 5 September 2008, Bologna N-folds area by tracks: AN(n) Poisson distribution Fig. 11 Evolution of track overlapping with fluence. Bologna, 2008 24 th Int. Conf. Nuclear Tracks in Solid

24 th International Conference on Nuclear Tracks in Solids 1 - 5 September 2008, Bologna Determination of the critical fluences for He and C Fig. 13 Changes in the absorbance at the first and the second peaks with helium ion fluence. Fig. 14 Changes in the absorbance at the first and the second peaks with carbon ion fluence. Bologna, 2008 24 th Int. Conf. Nuclear Tracks in Solid

24 th International Conference on Nuclear Tracks in Solids 1 - 5 September 2008, Bologna Determination of the critical fluences Fig. 15 Changes in the absorbance at the first and the second peaks with oxygen ion fluence. Fig. 16 Changes in the peak height ratio with ion fluence. Bologna, 2008 24 th Int. Conf. Nuclear Tracks in Solid

24 th International Conference on Nuclear Tracks in Solids 1 - 5 September 2008, Bologna AFM-method without etching Tracks of 80 Me. VAu ion in PMMA Bologna, 2008 24 th Int. Conf. Nuclear Tracks in Solid

24 th International Conference on Nuclear Tracks in Solids 1 - 5 September 2008, Bologna AFM-method OLYMPUS Nano. Vision 2000 Fig. 23 Assessed latent track radial size in PADC plastics for light ions and fission fragment indicating as a function of stopping power. Fig. 21 Etch pit radii for fission fragments and alpha-particles as a function of the etching time. RM 37 (2003)119 -125. Bologna, 2008 24 th Int. Conf. Nuclear Tracks in Solid

24 th International Conference on Nuclear Tracks in Solids 1 - 5 September 2008, Bologna Track core radius by IR-method Fig. 31 Relation between the track core radii and stopping power from the IR-method (GANIL&HIMAC). GANIL: Grand Accelerateur National d’Ions Lourds Bologna, 2008 24 th Int. Conf. Nuclear Tracks in Solid

24 th International Conference on Nuclear Tracks in Solids 1 - 5 September 2008, Bologna Track core radius in PC Fig. 33 Relation between the track core radii and stopping power in Rev FMS. KU 4 (2006)61 -70. PC from various methods. Bologna, 2008 24 th Int. Conf. Nuclear Tracks in Solid

24 th International Conference on Nuclear Tracks in Solids 1 - 5 September 2008, Bologna Tracks in PC Fig. 34 Relation between the track core radii and stopping power in PC. Fig. 35 Relation between the G value for loss of C=O and stopping power in PC. Almost independent of stopping power Bologna, 2008 24 th Int. Conf. Nuclear Tracks in Solid

24 th International Conference on Nuclear Tracks in Solids 1 - 5 September 2008, Bologna Tracks in PADC Fig. 41 Radial dose distribution of energy deposited around the path of heavy ions in PC. Fig. 42 Radial dose distribution of energy deposited around the path of heavy ions in PADC. Bologna, 2008 24 th Int. Conf. Nuclear Tracks in Solid

24 th International Conference on Nuclear Tracks in Solids 1 - 5 September 2008, Bologna Gamma-irradiated PADC Fig. 41 Decrease of the relative absorbance with gamma-dose. Fig. 42 G value for loss of carbonate ester bonds in gamma and heavy ion irradiated PADC. Bologna, 2008 24 th Int. Conf. Nuclear Tracks in Solid

24 th International Conference on Nuclear Tracks in Solids 1 - 5 September 2008, Bologna Summary 1/3 • A review was given for the present status of our study on track core radii for proton and heavy ions in PADC. • Evaluated core radii were dependent on the methods: UV, AFM, and IR-methods. Bologna, 2008 24 th Int. Conf. Nuclear Tracks in Solid