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Kimio Niwa* Toshiyuki Toshito** Ken'ichi Kuge*** Nakahiro Yasuda**** Mitsunori Natsume*

Kimio Niwa* Toshiyuki Toshito** Ken'ichi Kuge*** Nakahiro Yasuda**** Mitsunori Natsume* Noriyuki Saito*. Observation of latent image specks in nuclear emulsion for the purpose of precise estimation of local deposit energy. Hirotaka Kubota

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Kimio Niwa* Toshiyuki Toshito** Ken'ichi Kuge*** Nakahiro Yasuda**** Mitsunori Natsume*

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  1. Kimio Niwa* Toshiyuki Toshito** Ken'ichi Kuge*** Nakahiro Yasuda**** Mitsunori Natsume* Noriyuki Saito* Observation of latent image specks in nuclear emulsion for the purpose of precise estimation of local deposit energy Hirotaka Kubota Nagoya University F-lab. *Nagoya University **High Energy Accelerator Research Organization (KEK)‏ ***Chiba University ****National Institute of Radiological Sciences (NIRS)‏

  2. A point of nuclear fragmentation reaction 12C (nucleus)‏ 180MeV/n 150 m Nuclear emulsion : Three-dimensional track detector Study of fragmentation using nuclear emulsion • We study nuclear fragmentation reactions of carbon ions for the heavy-ion radiotherapy. • Precise measurement of the deposit energy. Micrograph of a fragmentation reaction recorded on a nuclear emulsion

  3. Exposure to a charged particle Deposition of energy to the silver bromide crystals A charged particle passes through silver bromide crystals Formation of Latent image specks Charged particle Silver bromide crystal（AgBr） Gelatin 0.2 m Latent image specks Track Figure of nuclear emulsion

  4. K. Kuge et al. Radiation Measurements 42 (2007) 1335-1341 Silver grain Silver bromide crystal １μm Normal photographic development Ag filaments are made from Ag+ ions in a AgBr crystal Ag filament Latent image speck Ag+ Silver bromide crystal (AgBr)‏ development fixation

  5. Au+ Latent image speck Au+ Au+ Au cluster K. Kuge et al. Radiation Measurements 42 (2007) 1335-1341 Gold cluster Silver bromide crystal (AgBr)‏ Silver bromide crystal development fixation １μm New technique = Gold deposition development Au grains are made from Au+ ions in the developer

  6. Low Deposit energy High Comparison Gold deposition development Normal photographic development Before development latent image speck Silver grain Gold cluster 1 1 1 1 3 3 5 1 5

  7. New estimation method We can count latent image specks (gold grains) one by one We can estimate deposit energy by line density of the number of latent image specks Range of developedsilver bromide Range of latent image specks Normal photographic development Gold deposition development

  8. Experiment Beam property • Exposure • Accelerator : HIMAC synchrotron at NIRS • Emulsion : OPERA film (made by Fujifilm)‏ • Beam : → • Density : 107 ions/cm2 • Development • Normal photographic development • Developer : XAA (made by Fujifilm)‏ • Temp. : 20℃ • Period : 25 minutes • Gold deposition development • Developer : → • Temp. : 23℃ • Period : 2, 5 days Formula for the gold deposition solutions • Used for the OPERA film • Developing agent is ascorbic acid

  9. Sample making for electron microscopes Plastic base Thickness : 0.5, 3.0m Incidence direction of the ions Slice with microtome Emulsion (After exposure and development)‏ Emulsion layer Used transmission electron microscope • JEM-2010 (acceleration voltage is 200kV) • H-1250ST : High Voltage Electron Microscope (1,000kV)

  10. Electron micrograph of carbon ion tracks(388MeV/n) • Group of latent image specks are in around 0.2m. • The size of the silver bromide crystals is 0.2m. • Plural latent image specks are formed in a silver bromide crystal. Period : 5 days Silver grain Gold cluster Silver grain Gold cluster 1m Normal photographic development Gold deposition development More number of latent image specks = more deposit energy

  11. Various ion tracks on electron micrograph 1mm H C C C Ar Fe 146 [MeV/n ] 276 113 51 463 419 9 [keV/mm] 52 93 166 389 804

  12. Raw data of the latent image specks number measurement He 146MeV/n C 51MeV/n C 276MeV/n Ar 463MeV/n C 113MeV/n Fe 419MeV/n

  13. Correlation of the number of latent image specks and deposit energy • Linear relationship in low deposit energy region. • Saturation in the region higher then 400keV/m. • Average number of latent image specks formed in one AgBr crystal is 3.6 in the region of saturation. (The number of AgBr crystals per 100m is 230.)‏

  14. Conclusion • We succeeded in making latent image specks visible with having kept the shape of the track. • Like a case of the light, A study of the latent image specks formation is enabled in the case of the charged particles. • The estimation of the deposit energy of the charged particles is enabled with one silver bromide crystal which is 0.2m size. • We developed the new measurement technique of the deposit energy by the line density of the number of latent image specks. • We showed that the deposit energy measurement was possible with latent image specks. • Because a plurality of latent image specks are generated on one silver bromide, the dynamic range of this measurement technique is wider than the conventional one.

  15. Low Low GD Deposit energy High High Estimation of deposit energy by grain density measurement Grain density (GD) = Line density of the number of developed silver grains Before development After development saturate

  16. The selection of the tracks Slice surface track Latent image specks on one silver bromide crystal are divided A slice To avoid picking up tracks on surface . . . Thickness of the slice : 0.5m → 3m (Thicker)‏ High Voltage Electron Microscope (H-1250ST) acceleration voltage : 1,000kV Stereoscopic observation

  17. Observation by stereo electron micrographs C 276MeV/n 1 m Three-dimensional observation is possible with a stereo glass. The tracks inside of the layer are picked up : The track which is chosen Side view : The track which is not chosen

  18. Broken by an electron beam Plastic base Emulsion layer Plastic base 21 mm (Before dev.) Plastic base Emulsion layer Emulsion layer Gelatine layer Gelatin layer

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