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The angular distribution and energy spectra of energetic protons emitted from a 5-μm thick copper tape target irradiated by p-, circularly-, and s-polarized 55-fs laser pulses with intensity of 8 – 9 × 10 18 W / cm 2 are measured. The protons are found in the rear target normal direction while the hot electrons are found in the laser propagation direction. The maximum energy of protons is equal to 1.34 MeV for p-polarized irradiation. The energy spectrum of protons depends strongly on the total amount of electrons but it does not so strongly depend on the electron angular distribution under our experiment conditions. Two-dimensional particle in cell simulations also show the maximal proton acceleration for the p-polarized pulse, less efficient acceleration for the circular polarization, and lower acceleration efficiency in the case of the s-polarization, which is related to the electron acceleration efficiency at the front side of the target.

A laser-driven proton beam with a maximum energy of a few MeV is stably obtained using an ultra-short and high-intensity Ti:sapphire laser. At the same time, keV X-ray is also generated at almost the same place where protons are emitted. Here, we show the successful demonstration of simultaneous proton and X-ray projection images of a test sample placed close to the source with a resolution of ~10 µm, which is determined from the source sizes. Although the experimental configuration is very simple, the simultaneity is better than a few hundreds of ps. A CR-39 track detector and imaging plate, which are placed as close as possible to the CR-39, are used as detectors of protons and X-ray. The technique is applicable to the precise observation of microstructures.

The capability of the CR-39 track detector for isotope identification was verified using 56Fe and 55Fe beams from the heavy ion accelerator HIMAC at NIRS. A CR-39 stack was exposed to 56Fe and 55Fe beams with the energies of 460 MeV/nucleon. Drastic improvements in the accuracies of microscopic image analysis and detector thickness measurement enabled us to identify those iron isotopes with high mass resolution using the CR-39 track detector. As a consequence of the reduction of systematic errors, the mass resolution for iron isotopes in the CR-39 detector was obtained to be 0.22±0.03 amu in rms. The mass resolution newly obtained by the CR-39 detector was compared with the former result and found to be 66% better than the former value of mass resolution as a result of reducing the systematic errors of mass dispersion. Moreover, the ultimate mass resolution of the CR-39 detector was estimated by calculation using those experimental results. As a consequence of reducing the random error, it is expected that the mass resolution for iron isotopes can ultimately approach to ~0.10 amu in the CR-39 detector.

A short-pulse (~210 fs) high-power (~1 TW) laser was focused on a tape target 3 and 5 µm in thickness to a size of 11×15 µm2 with an intensity of 3×1017 W/cm2. Protons produced by this laser with an energy spread of 100% were found to be improved to create peaks in the energy distribution with a spread of ~7% by the application of the RF electric field with an amplitude of ±40 kV synchronous to the pulsed laser. This scheme combines the conventional RF acceleration technique with laser-produced protons for the first time. It is possible to be operated up to 10 Hz, and is found to have good reproducibility for every laser shot with the capability of adjusting the peak positions by control of the relative phase between the pulsed laser and the RF electric field.

A highly collimated sub-MeV proton beam with the divergence angle of 10 degrees is obtained during the interaction of a few terawatt pulse from a table-top Ti:sapphire laser with a thin metallic foil. This beam is used for proton shadowgraphy. The quality of the 107 laminar protons per bunch is sufficient for good quality projection imaging of a micrometer size mesh structure, giving a quantitative characterization of the proton beam, such as the transverse emittance of less than 0.1 π mm mrad. These experimental results open up a new perspective in imaging techniques.

New optical system with an optical displacement sensor has been developed to measure the local thickness of CR-39 track detector. It can be applied to measure locally the thicknesses of whole detector area for making a map of the amount of bulk etch. The accuracy of the thicknesses measurement was found to be ± 0.2 μ m using CR-39 detector. This accuracy is one order of magnitude higher than that of conventional methods, such as the Micrometer method, and is comparable to that of track size measurement under the optical microscope. It will also greatly improve the charge and mass resolutions of CR-39 detector that we can apply to measure galactic cosmic rays (GCRs) nuclei, especially the trans-iron nuclei ( Z ⩾ 30 ) in GCRs.

We report, for the first time, that the energy of femtosecond optical laser pulses, E, with relativistic intensities I > 1021 W/cm2 is efficiently converted to X-ray radiation, which is emitted by “hot” electron component in collision-less processes and heats the solid density plasma periphery. As shown by direct high-resolution spectroscopic measurements X-ray radiation from plasma periphery exhibits unusual non-linear growth ~E4–5 of its power. The non-linear power growth occurs far earlier than the known regime when the radiation reaction dominates particle motion (RDR). Nevertheless, the radiation is shown to dominate the kinetics of the plasma periphery, changing in this regime (now labeled RDKR) the physical picture of the laser plasma interaction. Although in the experiments reported here we demonstrated by observation of KK hollow ions that X-ray intensities in the keV range exceeds ~1017 W/cm2, there is no theoretical limit of the radiation power. Therefore, such powerful X-ray sources can produce and probe exotic material states with high densities and multiple inner-shell electron excitations even for higher Z elements. Femtosecond laser-produced plasmas may thus provide unique ultra-bright X-ray sources, for future studies of matter in extreme conditions, material science studies and radiography of biological systems.

We have developed a multi-channel cross-correlator (MCCC) for single-shot measurement of temporal contrast of Peta-watt class laser pulse. We report experimental results with the MCCC system.

Experimental demonstration of multi-charged heavy ion acceleration from the interaction between the ultra-intense short pulse laser system and the metal target is presented. The laser pulse of

Objective Second primary malignancies have become the leading cause of death in retinoblastoma survivors. Although osteosarcoma is the most common second malignancy, little is known about its clinical and therapeutic features. Methods We retrospectively reviewed a database of patients with retinoblastoma and osteosarcoma occurring as a second malignancy between 1964 and 2010 at the National Cancer Center Hospital of Japan. Results Among 857 patients with retinoblastoma registered in the database, 10 (1.1%) developed osteosarcoma as a second malignancy. The median age at the onset of retinoblastoma was 3 months, being bilateral in nine patients and unilateral in one. Systemic chemoreduction was performed in three patients and intra-arterial chemotherapy in six; all patients received external beam radiotherapy. The median age at the onset of second primary osteosarcoma was 11.2 years; four were radiation-related and six were located in an extremity. Among five patients treated at our institute, four patients with tumors on an extremity were treated by wide resection with neoadjuvant and adjuvant chemotherapy. Three of these four patients (75%) were good responders to high-dose methotrexate-based multi-agent chemotherapy and survived with no evidence of disease (median follow-up period, 17.3 years). One patient whose temporal bone was affected underwent radiotherapy with chemotherapy but died after local recurrence. Conclusions The clinical outcomes of second primary osteosarcoma in an extremity occurring in retinoblastoma survivors may be more favorable than those of conventional osteosarcoma. Early diagnosis of radiation-related osteosarcoma arising in the craniofacial region should be made at a stage where complete resection is possible.

We observe the electron density distribution of preformed plasmas of a titanium foil target with the 400 nm probe beam as an interferometer. The preformed plasma at the front side of the target is generated by a prepulse with a high-intensity Ti:sapphire laser. On the other hand, the preformed plasma at the rear side is not observed within the region ∼18 μm away from the original surface. The characterization of preformed plasmas will contribute to describe the high-intensity laser and thin-foil interactions.

We report the experimental results of proton acceleration as well as the simple one-dimensional model which explains our experimental data. The proton acceleration experiment is carried out with a TW short pulse laser irradiated on a tantalum thin-foil target (3 μm thickness) with an intensity of ∼ 3 × 10 18 W cm −2 . Accelerated protons exhibit a typical energy spectrum with two quasi-Maxwellian components with a high energy cut-off. We can successfully explain the higher energy part as well as the cut off energy of the proton spectrum with the simple-one-dimensional model based on the strong charge separation regime, which is the extension of the model proposed originally by [M. Passoni et al., Phys. Rev. E 69 (2004) 026411].

A scheme of the real-time optimization of proton production by an intense short-pulse laser interacting with a foil target was developed using a time-of-flight measurement with a plastic scintillator. Owing to special treatments, the detection of protons using a scintillation counter has become possible under heavy backgrounds such as laser light itself, laser-generated hard X-ray, self-emission light, and electrons from the laser-produced plasma. With such a real-time measurement of protons, the energy spectrum of protons could be obtained shot by shot, and the experimental conditions for optimal proton production could be determined very efficiently.

We developed a beam-pointing stabilizer for a 10-TW Ti:sapphire laser system to study laser-induced ion acceleration. We confirmed the improvement in the laser beam pointing stability by using a 10-TW laser system (we call it JLITE-X) at JAERI-APRC. The original long-term pointing stability on a 10-TW laser system is ∼70 μrad without beam stabilizing. By using a beam-pointing stabilizer, the laser beam stability was improved within 10 μrad. If f/1 focusing optics and a target which is tilted 45° to the target normal is used, the fluctuation of the laser intensity at the focus will be improved from 80% without stabilizing to

A two-color interferometer for preformed plasma characterization is developed. We observe the electron density distribution of preformed plasmas on a 5 μm-thick copper target irradiated with a high-intensity Ti:sapphire laser. The two-color interferometer extended the observable electron density region using a fundamental (800 nm) probe beam to cover the lower density region and a second harmonic (400 nm) probe beam to cover the higher density region, simultaneously. This characterization of the electron density distribution of preformed plasmas with femtosecond time resolution significantly contributes to the understanding of high-intensity laser–thin-foil interactions during high-energy electron, ion, and X-ray generation.

In order to widely spread out particle beams utilized in cancer therapy, laser-produced ions are developed as the injection beam for an ion synchrotron dedicated for cancer therapy. Such a laser ion source is expected to contribute largely to the realization of compactness of the size and low cost of the cancer therapy accelerator. The energy spectrum of the laser-produced ions, however, has no peak, but their intensities decrease exponentially according to the increase of the energy. For the purpose of modifying such a situation, we have proposed a scheme to rotate the beam in the longitudinal phase space with the use of the RF electric field, which is phase-adjusted with the pulse laser. We aim for a reduction of the energy spread of ± 5% selected by an energy analyzer and slits to ±1% by such phase rotation. For this purpose, a quarter wavelength resonator with two gaps with the same resonant frequency as the source laser has already been fabricated, together with its RF power source. The above phase rotation system and its recent experimental realization are presented.

In this paper, we present the motivation and future prospects of the laser-driven proton generation and its application to the medical accelerators. Then we present the experimental results of the high energy proton beam produced by a Ta 3 μm target irradiated with a 3 × 1018 W cm-2, ~70 fs pulse laser. The measured proton spectra can be divided into three parts; low-energy, high-energy, and cut-off. We propose the possible acceleration mechanism which describes our data, and the resultant problems which we should solve to reach our objectives.

In radiation cancer therapies using energetic charged particles such as proton/heavy-ion therapy and boron neutron capture therapy (BNCT), studies on radiation-induced biological response at cellular level are important because the radiation damage from energetic charged particles is highly localized along their paths and the radiation sensitivity is quite different in each cellular organelle. In such studies the information on the position of charged particle impact in biological cells is necessary. A novel method for high-resolution nuclear track mapping in detailed cellular histology has been developed. In this technique, biological specimens mounted on CR-39 plates are exposed to energetic charged particles. The irradiated samples are exposed to UV, and then etched for a short time. Both etch pits of nuclear tracks and relief for transmission UV image of the specimen can be observed on the CR-39 surface with an atomic force microscope (AFM) at about 100 nm resolution.

Soft X-ray microscopy using CR-39 plastic track detectors was demonstrated with an atomic force microscope (AFM) readout for the first time. A transmission X-ray image of the biological cells was recorded on the CR-39 surface, and revealed as relief after etching process. The resolution of the X-ray imaging is expected to be 100 nm or less, therefore imaging of biological cells is possible at an intracellular structure level. Using this technique, the high resolution image of both biological cells and charged particle tracks can be obtained simultaneously on a CR-39 with the AFM. In boron neutron capture therapy, this new technique provides the information on the distribution of boron compounds and radiation dose by charged particles mapping inside a cell.

We report on the spectra of x-rays emitted from dense plasma generated via irradiation of thin stainless steel foils by ultra-relativistic femtosecond laser pulses (intensities ~3 × 10^21 W/cm^2). Kinetic modelling was used to estimate electron plasma density and temperature, demonstrating Te ~2.1 keV for Ne ~5 × 10^22 cm^−3 in the hottest emission region. Thus, it is experimentally demonstrated for the first time that the laser pulse of over 10^21 W/cm^2 intensity is absorbed neither in the solid density plasma nor in a pre-plasma of a common critical density, but in the matter of so called relativistic critical density.

Objective:Boron neutron-capture therapy (BNCT) has been used to inhibit the growth of various types of cancers. In this study, we developed a 10BSH-entrapped water-in-oil-in-water (WOW) emulsion, evaluated it as a selective boron carrier for the possible application of BNCT in hepatocellular carcinoma treatment.Methods:We prepared the 10BSH-entrapped WOW emulsion using double emulsification technique and then evaluated the delivery efficacy by performing biodistribution experiment on VX-2 rabbit hepatic tumour model with comparison to iodized poppy-seed oil mix conventional emulsion. Neutron irradiation was carried out at Kyoto University Research Reactor with an average thermal neutron fluence of 5 × 1012 n cm−2. Morphological and pathological analyses were performed on Day 14 after neutron irradiation.Results:Biodistribution results have revealed that 10B atoms delivery with WOW emulsion was superior compared with those using iodized poppy-seed oil conventional emulsion. There was no dissemination in ab...

Introduction. Although several intercalary reconstructions after resection of a lower extremity malignant bone tumor are reported, there are no optimal methods which can provide a long-term reconstruction with fewest complications. We present the outcome of reconstruction using a devitalized autograft and a vascularized fibula graft composite.Materials and Methods.We conducted a retrospective review of 11 patients (7 males, 4 females; median age 27 years) undergoing reconstruction using a devitalized autograft (pasteurization (n=6), deep freezing (n=5)) and a vascularized fibula graft composite for lower extremity malignant bone tumors (femur (n=10), tibia (n=1)).Results. The mean period required for callus formation and bone union was 4.4 months and 9.9 months, respectively. Four postoperative complications occurred in 3 patients: 2 infections (1 pasteurized autograft, 1 frozen autograft) and 1 fracture and 1 implant failure (both in pasteurized autografts). Graft removal was required in 2 patients with infections. The mean MSTS score was 81% at last follow-up.Conclusions.Although some complications were noted in early cases involving a pasteurized autograft, our novel method involving a combination of a frozen autograft with a vascularized fibula graft and rigid fixation with a locking plate may offer better outcomes than previously reported allografts or devitalized autografts.

Multimodality therapy has greatly improved the prognosis of patients with localized osteosarcoma, over 50% of patients remaining free of disease for up to 5 years after treatment [1e4]. Most relapses, especially in the form of early pulmonary metastasis, usually occur within 2e3 years after treatment. Relapse after 5 years is uncommon and has been described only infrequently [1e7]. Low-grade central osteosarcoma is a rare subtype of osteosarcoma, accounting for 1e2% of all osteosarcomas [8,9]. Although its prognosis is excellent, with 90% overall survival at 5 years [8], some cases of late metastasis have been reported, and this may continue to impact survival even after 10 years [10]. Here we report a case of lung metastasis that occurred 17 years after initial treatment of low-grade central osteosarcoma of the distal femur. Radiologic evaluation revealed atypical pleural thickening with calcification, spreading inward along with the peripheral pulmonary vasculature. Since the presentation and radiologic manifestation of metastasis in this case were extremely unusual, and demographic data are an essential part of diagnosis, the

Introduction In patients undergoing limb-salvage internal hemipelvectomy, pelvic ring reconstruction is mandatory to maintain the stability of the pelvis and the spinal column, which finally expected to achieve a good functional outcome. However, no optimal reconstruction method has been established. In addition, no previous reports have highlighted the long-term complications of pelvic ring reconstruction after internal hemipelvectomy. We aimed to analyze the outcome of pelvic ring reconstruction using a double-barreled free vascularized fibula graft (VFG) after internal hemipelvectomy with special reference to long-term complications. Materials and methods We conducted a retrospective review of 9 consecutive patients (5 male, 4 female; mean age 31 years) who underwent pelvic ring reconstruction using a double-barreled free VFG after internal hemipelvectomy (P1, n = 4; P1 + 4, n = 3; P1 + 2, n = 2) at our institution between 1998 and 2013. The mean follow-up period was 55 months (range 3–131 months). Results The mean length of the bone defect was 9 cm. The methods of fixation included a Cotrel-Dubosset rod (n = 4), screw (n = 3), and screw and plate (n = 2). Bone union was achieved in 5 of 8 patients (63 %) over a 1-year follow-up. The mean period required for bone union was 5.4 months (range 3–7 months). There were 3 early postoperative complications: 2 deep infections resulting in graft removal and 1 implant failure resulting in non-union. Among 3 patients, 2 developed scoliosis within 5 years. One patient developed lumbar disc hernia as a result of scoliosis, for which surgical intervention was required. The mean Musculoskeletal Tumor Society score was 57 % at the last follow-up. Conclusions In conclusion, this reconstruction method can achieve an early and high rate of bone union and provide good functional outcome. However, follow-up with careful attention to postoperative complications, including deep infection in the early postoperative period and spinal deformity in the long term, is necessary.

Introduction Chronic expanding hematoma is a rare persistent hematoma that can sometimes be misdiagnosed as a malignant tumor due to its clinical and radiological features. Case presentation A 42-year-old Japanese man with a large mass in his leg, suggestive of malignancy, presented to our hospital. He had been aware of the leg swelling for the last eight years. A magnetic resonance imaging scan demonstrated a large mass with two components. One was a large, well-defined cystic mass (13×9cm) showing high intensity on T1- and T2-weighted images, and the other was a solid mass (3.5×2.5cm, adjacent to the large mass) with high intensity on T1-weighted images. Two-[18F]fluoro-2 deoxy-D glucose positron emission tomography images revealed increased uptake with a maximum standardized uptake value of 15.8 in the solid mass. As these findings were considered suggestive of hematoma associated with a malignant lesion, an open biopsy was performed. A pathological examination demonstrated a hematoma with xanthogranuloma, and no malignant cells were evident. Therefore, we resected the tumor including both components, and the histological diagnosis was chronic expanding hematoma. Clinical diagnosis based on 2-[18F]fluoro-2 deoxy-D glucose uptake is sometimes limited by the fact that 2-[18F]fluoro-2 deoxy-D glucose is taken up by not only malignant tumor cells but also macrophages and tissues with granulation or inflammation. Conclusions Significantly increased standardized uptake value in the peripheral rim of the lesion on 2-[18F]fluoro-2 deoxy-D glucose positron emission tomography imaging, mimicking a soft tissue sarcoma, should be recognized as a potential diagnostic pitfall in cases of chronic expanding hematoma.

High intensity laser-plasma interaction has attracted considerable interest for a number of years. The laser-plasma interaction is accompanied by generation of various charged particle beams, such as high-energy proton and ions with high charge to mass ratio (Q/M; same as multi-charged ions). Results of simultaneous novel measurements of electron-induced photonuclear neutrons (photoneutron), which are a diagnostic of the laser-plasma interaction, are proposed to use for optimization of the laser-plasma ion generation. The proposed method is demonstrated by the laser irradiation with the intensity of 1 × 10(21) W/cm(2) on the metal foil target. The photoneutrons are measured by using NE213 liquid scintillation detectors. Heavy-ion signal is registered with the CR-39 track detector simultaneously. The measured signals of the electron-induced photoneutrons are well reproduced by using the Particle and Heavy Ion Transport code System. The results obtained provide useful approach for analyzing the various laser based ion beams.

Experimental demonstration of multi-charged heavy ion acceleration from the interaction between the ultra-intense short pulse laser system and the metal target is presented. Al ions are accelerated up to 12 MeV/u (324 MeV total energy). To our knowledge, this is far the highest energy ever reported for the case of acceleration of the heavy ions produced by the10 J laser energy of 200 TW class Ti:sapphire laser system. Adding to that, thanks to the extraordinary high intensity laser field of ∼10(21) W cm(-2), the accelerated ions are almost fully stripped, having high charge to mass ratio (Q/M).

Almost fully stripped aluminum ion acceleration up to 12 MeV/u from the interaction between the ultra-intense short pulse high contrast laser and the micrometer thick foil target is presented.

We have developed a new plastic track etch detector labeled TNF-1, which is the copolymer of CR-39 monomer with N-isopropylacrylamide (NIPAAm). It was found that copoly(CR-39/NIPAAm/ antioxidant) composed in weight ratio of 99/1/0.01 is highly sensitive to low linear energy transfer (LET) particles in the region below 10 keV/μm of LET200 eV. TNF-1 is the most sensitive plastic track etch detector reported so far and is able to record normally incident protons up to the energy of 27 MeV. This paper gives results of our studies on the track responses of TNF-1 as well as the brief results obtained by the performance tests of TNF-1 in various dosimetric experiments such as space radiation dosimetry, dosimetry for heavy ion cancer therapy and neutron dosimetry. These results are compared with the results obtained for CR-39 track detectors.

We have measured the total and partial charge-changing cross-sections (Z=5) after the passage of a 110 MeV / u 12 C beam through an assembly consisting of CR-39 thin detectors and paraffin targets. These experimental cross-sections were compared to the predictions of known models. It was found that the measured total cross-sections agree with the model calculations to within about 8% or even less, while, depending on a model, discrepancies of up to a factor 1.2 higher and up to a factor 2.7 lower values of cross-sections for the production of fragment with Z=5 were observed.

As a frame work of the study for the latent track size measurement using atomic force microscope, we have measured the minute etch pits and the extremely small amount of bulk etch of CR-39 at the beginning of chemical etching, and obtained its growth curves in nanometer dimensions. The pieces of CR-39 were exposed to 6 MeV / n C and Fe ions with normal incidence angle and were etched in 70°C 7 N NaOH solution for 0.5,1,2,3,5 min . The diameters of latent track were estimated to be ∼17 nm for Fe ions and ∼8 nm for C ions, respectively. These values are comparable to the experimental data on the average ‘track core diameters’ that have been obtained by various experimental techniques.

For the study on boron neutron capture therapy, CR-39 plastic track detectors attached with the whole-body sections of tumor bearing mice infused with 10 B were exposed to thermal and cold neutron beams. Neutron capture autoradiographic images obtained by the cold neutron irradiation were extremely superior in quality than that of the thermal neutron beams, which possibly are contaminated by the fast neutron component. The LET distributions of the neutron-induced particles suggested that the fast neutron component was considerably included in the thermal neutron beams used in this study. In addition, the quality of radiographic images obtained by PEW etching is compared with the images on CR-39 etched in a NaOH solution.

The temporal contrast of an ultrahigh-intensity laser is a crucial parameter for laser plasma experiments. We have developed a multichannel cross-correlator (MCCC) for single-shot measurements of the temporal contrast in a high-power laser system. The MCCC is based on third-order cross-correlation, and has four channels and independent optical delay lines. We have experimentally demonstrated that the MCCC system achieves a high dynamic range of ∼1012 and a large temporal window of ∼1 ns. Moreover, we were able to measure the shot-to-shot fluctuations of a short-prepulse intensity at −26 ps and long-pulse (amplified spontaneous emission, ASE) intensities at −30, −450, and −950 ps before the arrival of the main pulse at the interaction point.

It is necessary for effective boron neutron capture therapy (BNCT) to accumulate 10 B atoms in the tumor cells. We prepared a cationic liposome entrapped 10 B compound for the delivery system and examined the delivery capacity of 10 B atoms to pancreatic cancer cell, AsPC-1, in vivo. It is required to achieve an accurate measurement of 10 B distributions and concentrations in biological samples with a sensitivity in the ppm range for BNCT. We applied CR-39 (polyallyldiglycol carbonate) plastic track detectors to α-autoradiographic measurements of the 10 B biodistribution in sliced whole-body samples of mice. To selectively desensitize undesirable proton tracks, we applied PEW (KOH+C2H5OH+H2O) solution to the etching of CR-39 detector. The subsequent use of an alpha-track radiographic image analysis system enabled a discrimination between alpha tracks and recoiled proton tracks by the track size selection method. This enabled us to estimate quantitatively the distributions of 10 B concentrations within the tissue sections by comparing with suitable standards.

We have developed an ultra-high resolution charged particle radiography technique using CR-39 solid state track detectors and an atomic force microscope (AFM). Very small etch pits about 80 nm in diameter were measured with the AFM. We planned to apply this technique to high resolution autoradiography. Such practical applications often require accurate positioning between the sample mounted on a CR-39 detector and particle tracks recorded in the CR-39 in order to determine the radiation dose distribution inside the sample. As a fiducial marker for the positioning, aluminum patterns were deposited on the CR-39 surface using a photolithography technique. The aluminum patterns were dissolved through a typical etching process for CR-39 detectors and pattern-shaped steps were left on the surface. Using these patterns should ensure accurate positioning between the sample and the etch pits in autoradiography. This method provides a new technique for radiation imaging of biological samples at a subcellular scale.

It is required to achieve an accurate measurement of 10 B distributions and concentrations in the tumor cells for boron neutron capture therapy (BNCT). We employed a technique of neutron capture autoradiography (NCAR) of the whole body samples of tumor bearing mice using CR-39 plastic track detectors to the measurements of 10 B accumulations in mice. In order to confirm the validity of the NCAR measurements, the differential REL spectrum for the neutron-induced particles emitted from the standard filter paper sheets was compared with that for 10 B-compound solution. Differential REL spectrum for protons originated from the biogenically abundant nuclides through 14 N (n, p) 14 C and 1 H (n, n′) 1 H reactions was measured in vivo using a small piece of CR-39 inserted into the tumor of mouse.

Atomic Force Microscope (AFM) has been applied to evaluate the surface roughness and the track sensitivity of CR-39 track detector. We experimentally confirmed the inverse correlation between the track sensitivity and the roughness of the detector surface after etching. The surface of CR-39 (CR-39 doped with antioxidant (HARZLAS (TD-1)) and copolymer of CR-39/NIPAAm (TNF-1)) with high sensitivity becomes rough by the etching, while the pure CR-39 (BARYOTRAK) with low sensitivity keeps its original surface clarity even for the long etching.

The track evolution for high energy C and Si ions in CR-39 was studied using an atomic force microscope (AFM). The image processing method of AFM observations and the 3-D images of C and Si tracks are reported. The track diameter increased linearly with the amount of bulk etch of CR-39, but the retardation of growth of the track length was observed at the early stage of the etching. As a result, considerable discrepancies between the track sensitivities calculated by using the track diameter and the length appeared especially in the early stage of the etching. The results reported here show that AFM observations are very useful in practical application to the quantitative analysis for minute etch pits in a track detector.

A new technique of selective enhancement and evaluation of radiographic images in etched track detectors was developed. It is based on the image processing of individual image element units – etched tracks – by a track analysis system. A selective radiograph is obtained on the basis of the assessment of the size and optical properties of individual tracks. The computer-generated image, in addition to its selectivity, which enables, for instance, multi-elemental analysis from an autoradiograph, also offers a contrast enhancement for better visual observation and/or evaluation. The applicability of the technique is illustrated by selective imaging of 10 B distribution in a whole body samples of a tumour-bearing mouse.

For atomic force microscope (AFM) observations of minute tracks ( ⩽1 μ m) in the CR-39 track detector, an accurate method to measure an extremely small amount of bulk etch is required. A simple method for direct measurements of the bulk etch using AFM was developed. Before the etching, a part of the CR-39 surface was covered with epoxy adhesive resin. The amount of bulk etch was measured as a level difference between the etched surface and the unetched original surface which has been covered with epoxy resin during its chemical etching processing. The details of this method are reported and its limitations are discussed in comparison to a conventional measuring method using tracks of fission fragments.

We present experimental results on protons accelerated up to 950 keV from a 3-μm thick tantalum foil with a 133-nm thick polystyrene layer on its rear surface, irradiated with a laser pulse having the duration of 70 fs and the intensity of 2.7×1018 W/cm2. The energy distribution of fast protons was measured simultaneously with that of the hot-electrons from the rear surface. The proton yield from the polystyrene-coated target is about 10 times as high as that from the uncoated metal target. This enhancement of the proton yield is roughly proportional to the increase of hydrogen atoms given by the 133-nm thick polystyrene layer, assuming a contaminant layer of ∼10-nm thickness is on the metal surface without coating. This result shows that the polystyrene layer contributes to the yield enhancement.

We studied the track response for the copolymer of CR-39 monomer with N-isopropylacrylamide (NIPAAm) as well as etching properties. It was found that copoly (CR-39/NIPAAm/Naugard 445) composed in wieght ratio of 99/1/0.01 is highly sensitive to low LET particles in the region below 10 keV/μm of LET 200 eV and able to record normally incident particles of LET 200 ev down to ∼1.5 keV/μm, recording protons up to the energy of 27 MeV. These results were compared with the responses for two types of CR-39 detectors containing a small quantity of antioxidant. The threshold energy proton registration is discussed.

Intelligent chemical valves responding to a slight change of temperature were created by the combination of ion beam-chemical etching technique and a novel material consisting of an ion track detector material diethyleneglycol-bis-allylcarbonate (CR-39) and a thermo-responsive gel acryloyl-L-proline methyl ester (A-ProOMe). The changes in size of ion-track pores in etched films were measured microscopically by repetition between 0 and 30°C at 24-h intervals for a 50 μm thick copoly(CR-39/A-ProOMe, 60 40 mol % ) film which was obtained by etching in aqueous 6M NaOH solution at 60°C after an 11.6 MeV/n 208Pb ion irradiation and, as a result, it was found that the pore size in the film obtained by etching for 10 min is reversibly changed from a perfectly closed pore at 0°C to a fully opened pore with a diameter of 0.30 μm at 30°C.

Preliminary results of feasibility study to apply atomic force microscope (AFM) to the quantitative analysis for minute etch pits on CR-39 are reported comparing with the optical microscope observation. The growth curves of the Si track diameter and length obtained by both technqiues were discussed in relation to the track sensitivity and the etch induction time.

Absolute Kα line spectroscopy is proposed to study laser-plasma interactions taking place in cone-guided fast ignition targets. A transmission-type spectrometer was developed, and its absolute sensitivity was measured with laser-generated x-rays and radioisotopes, showing good agreement with theoretical predictions. The absolute yield of Au Kα line was mesured in the fast ignition experimental campaign perfomed at ILE, Osaka University. Assuming a single Maxwellian electron spectrum and one-way travel of hot electrons through the cone, energy transfer efficiency of incident LFEX laser to hot electrons was derived.

Kα line emission from Mo was experimentally and theoretically studied using clean, ultrahigh-intensity femtosecond laser pulses. The absolute yields of Kα x-rays at 17 keV from Mo were measured as a function of the laser pulse contrast ratio and irradiation intensity. Significantly enhanced Kα yields were obtained by employing high contrast ratio at optimum irradiance. Conversion efficiencies of 4.28 × 10 −5 /sr, the highest values obtained to date, was demonstrated with contrast ratios in the range of 10 −10 to 10 −11 .