ABSTRACT 1. INTRODUCTION

Transcription

1 Iwamura, Y., T. Itoh, ad M. SakaNo. Nuclear Products ad Their Time Depedece Iduced by Cotiuous Diffusio of Deuterium Through Multi-layer Palladium Cotaiig Low Work Fuctio Material. i 8th Iteratioal Coferece o Cold Fusio Lerici (La Spezia), Italy: Italia Physical Society, Bologa, Italy. NUCLEAR PRODUCTS AND THEIR TIME DEPENDENCE INDUCED BY CONTINUOUS DIFFUSION OF DEUTERIUM THROUGH MULTI-LAYER PALLADIUM CONTAINING LOW WORK FUNCTION MATERIAL Yasuhiro IWAMURA, Takehiko ITOH ad Mitsuru SAKANO Advaced Techology Research Ceter, Mitsubishi Heavy Idustries, Ltd , Sachiura, Kaazawa-ku, Yokohama, , Japa iwamura@atrc.mhi.co.jp ABSTRACT Two kids of experimetal methods have bee desiged to iduce uclear reactios i the Pd-D system. Oe is the D gas diffusio method, ad the other is the electrolysis diffusio method. A commo feature of the methods is to cause cotiuous diffusio of deuterium through a multi-layer Pd that cotais low work fuctio material (CaO, TiC, YzOs, etc.). Time depedece of uclear products (Mg, Si, S, F, Al) were observed by the D gas diffusio method, i which the products were aalyzed WITHOUT takig the multi-layer Pd out of the apparatus. The time depedece of the products was reproduced qualitatively. The 33 S/ 3 S ratio of the products was oe order larger tha that of atural abudace. Fe isotope ratio aomaly of the multi-layer Pd obtaied by the electrolysis diffusio method was cofirmed by SIMS ad TOF-SIMS. Si powder products detected after electrolysis amouted to 0.057g, ad its isotopic compositio was aomalous. 1. INTRODUCTION Nuclear reactios observed i the low eergy deutero ad metal system have bee ivestigated itesively. However, the ature of the pheomea is still uclear. Our experimetal results so far lead us to assume that ecessary coditios to iduce uclear reactios i solids are as follows; (i) existece of a low work fuctio material ear the Pd surface, (ii) eough diffusio flux of deuterium, (iii) high D/Pd o the Pd surface. To meet with the assumptios, we have cotrived two kids of experimetal methods characterized by multi-layer Pd ad cotiuous difusio of D as show i Fig. 1. The multi-layer Pd cosists of Pd thi film, low work fuctio material ad Pd bulk. It correspods to the assumptio (i). Eough diffusio flux of deuterium, assumptio (ii), is satisfied with the compositio show i the lower figure. Deuterium atoms are provided with D electrolyte or D gas ad released from the vacuum side. They are cotrollable by the applied electric curret or D gas pressure. As for the assumptio (iii), eough D/Pd ratio o the Pd thi film is cosidered to be attaied by our methods.

2 . Experimetal Figure show the cross sectioal view of the D gas diffusio apparatus. The feature of this method is that it ca aalyze the surface of a Pd sample by XPS (X-ray Photoelectro Spectroscopy) WITHOUT takig it out of the apparatus. Therefore it is possible to avoid cotamiatio oto the Pd sample from outer eviromet. This ewly developed apparatus ca provide the data of time depedece of detected uclear products. The apparatus cosists of two vacuum chambers, a X-ray gu ad a electrostatic aalyzer for XPS, a mass spectrometer ad a Ge semicoductor detector. Oe chamber is filled with D gas, ad the other chamber is evacuated by a turbo molecular pump. These two chambers are divided by a multi-layer Pd composed of Pd thi film (400 agstrom), low work fuctio layer (typically CaO; 1000 agstrom) ad Pd sheet (5mm 5mm 0.1mm). The experimetal procedure is as follows. First, the surface of a multi-layer Pd i the vacuum chamber is aalyzed by XPS to cofirm that the surface of the Pd sample is clea. Next, D gas is allowed ito a chamber ad deuterium atoms diffuse from the D side chamber to the vacuum side chamber. At this momet a uclear reactio occurs o the multi-layer Pd cotaiig low work fuctio material. After certai period (from days to 1 week) of deuterium diffusio through the Pd sample, the D side chamber is evacuated ad the surface of the Pd sample is aalyzed by XPS i the chamber. New elemets, which did ot exist o the Pd sample at the begiig of the experimet, ca be detected. To obtai a time depedece aalysis of the products, the process is repeated 3 to 4 times. Fig. 1. Features of the Preset Method Experimetal results usig the electrolysis type of apparatus were preseted at ICCF-7[1]. Schematic view of the electrolysis diffusio method is show i Fig. 3. Details of the apparatus are give i refereces [1] ad []. The feature of this apparatus is that much larger reactio rate is possible because D/Pd o the Pd surface is larger tha that of D gas diffusio method. We ca estimate excess heat ad radiatio with this type of apparatus, although elemet ad mass aalysis of the Pd sample become possible after the ed of a experimet.

3 Fig.. D Gas Diffusio Method Fig. 3. Electrolysis Diffusio Method 3. RESULTS AND DISCUSSION Experimetal results by the D diffusio method are show i Fig We tried three kids of materials; ormal Pd, multi-layer Pd (Pd/CaO/Pd) ad Li doped multi-layer Pd (Pd,Li/CaO/Pd). Figure 4 shows the time depedece of C o the ormal Pd (Pd oly) sample which existed as a impurity at the begiig of the experimet. C usually exist o the surface of a Pd sample uless we remove it. Therefore, C ad Pd are detected by XPS o the ormal Pd sample. The umbers of C atoms detected by XPS did ot chage for two cases (No. 1, ), although the iitial C ad experimet time were differet each other. No time depedece of C was observed if Pd-oly samples were used.

4 Fig. 4. Time Depedece of C (impurity) detected o the Pd oly samples Multi-layer Pd gave us etirely differet results. Time depedece of C, Mg, S, Si o the multi-layer Pd (Pd/CaO/Pd) is show i Fig. 5 First, we will explai the result of experimet No. 3. There were o elemets except C ad Pd at the begiig of the experimet. No Mg, Si ad S existed o the sample. Mg, Si ad S peaks emerged ad the C peak decreased after 4 hours of deuterium diffusio through the multi-later Pd. At 116 hours, S ad Si icreased ad Mg decreased. As for No. 4 experimet, amout of C was slightly larger tha that of No. 4. Mg, Si ad S were detected agai after 4 hours. After that, Mg decreased, Si ad S icreased, ad C decreased mootoically as show i the figure o the right. These results idicated that the behavior of C, Mg, S, Si were reproduced qualitatively. Fig. 5. Time Depedece of C, Mg, Si, S detected o the Pd/CaO/Pd samples Examiatio o isotope ratio of the detected elemets was carried out. Table 1 shows compariso betwee multi-layer Pd ad ormal Pd o isotopic abudace of S. Samples No. 1 ad No. 4 were aalyzed by SIMS (Secodary Io Mass Spectroscopy) after the experimets. S o the No. 1 sample was detected by SIMS, although o S was detected by XPS. Sice the sesitivity for S of SIMS is higher tha that of XPS, S o the No. 4 sample was observed by both XPS ad SIMS. As for 36 S, o effective couts were obtaied because abudace of 36 S is very small.

5 Although secodary io itesity of the No. 4 was larger tha that of the No. 3, 34 S/ 3 S was almost equal to each other. 34 S/ 3 S is early equal to the atural abudace. O the other had, 33 S/ 3 S of the Pd/CaO/Pd (No. 4) was oe order larger tha that of Pd oly (No. 1). 33 S/ 3 S of the No. 1 was early equal to the atural abudace. These results show i Table 1 idicate that isotopic abudace of S o the multi-layer Pd (No. 4) was aomalous ad S o the ormal Pd seemed atural. Table 1. Compariso betwee Multi-layer Pd ad Normal Pd o Isotopic Abudace of S Type of Sample Secodary Io Itesity (cps) Isotope Ratio S S S S/ 3 S 34 S/ 3 S Pd/CaO/Pd (No. 4) Pd Oly (No. 1) Natural Abudace Let us discuss o the above experimetal results o the multi-layer Pd. The first poit is the time depedece of C, Mg, Si, S. These elemets were detected by XPS without takig the multi-layer Pd out of the vacuum chamber. The surface of the sample was just oly exposed with D gas. Therefore it was difficult to add these elemets o the surface of the multi-layer Pd, or remove them from it. Especially Mg oce icreased ad decreased. It is very difficult to explai their behaviors by certai cotamiatio processes. The secod poit is that product S had aomalous isotopic abudace. As show i Table 1, 33 S/ 3 S is oe order larger tha atural isotope ratio. If the S were cotamiatio, was such efficiet isotope separatio possible? Accordig to the poits, we ca coclude that it is strogly suggested that Mg, Si, S are formed by certai uclear reactios. If these elemets are uclear products, they are basically explaied by the EINR (Electro-Iduced Nuclear Reactio) model[]. Experimetal results eable us to make a iterpretatio that C was trasmuted to Mg, Si, S. The EINR model gives the followig explaatio. At first deuterium uclei capture electros ad form di-eutro clusters. Simultaeously, the di-eutro clusters react with C, ad produce Mg. After that, Mg reacts with di-eutro clusters agai ad is trasmuted ito Si or S. 0 1 d 1e 0 v (1) C C Mg Mg Si S I the Pd/CaO/Pd experimets, impurity C was trasmuted ito Mg, Si, S. The ext experimets were performed aimig to trasmute Li ito other elemets. () (3)

6 Fig. 6. Time Depedece of F, Mg, Al, Si detected o the Pd, Li/CaO/Pd samples Experimetal results o Li doped multi-layer Pd are show i Fig. 6. Lithium atoms were doped by the electrolysis of LiOD solutio oto the surface of the multi-layer Pd (Pd/CaO/Pd). The ew elemets F, Al emerged i the both cases, No. 5 ad No. 6. F iitially icreased ad the decreased. Al icreased mootoically. The behaviors of F ad Al were similar to Mg ad Si, respectively, though the emergece time of F ad Al i the case of No. 5 is differet. Mg ad Si are cosidered to have origiated from impurity C. We observed F ad Al by addig Li o the surface of multi-layer Pd, therefore we assume that F ad Al were trasmuted from the added Li as show i the followig equatio Li 9 F Al At preset, the model is theoretically icomplete. However, it is oticeable that the similar explaatio is possible betwee the trasmutatios of C ad Li. (4) Fig. 7. Fe Isotope Aomaly observed by TOF-SIMS Next, experimetal results obtaied by the electrolysis diffusio method are described. Excess heat ad uclear products were observed for almost all the cases we tried usig the multi-layer Pd. Isotopic compositio of the obtaied product were ofte differet from atural abudace. The authors usually estimate the isotopic compositio of a

7 product by SIMS. Figure 7 presets a example i which the Fe isotope ratio aomaly was cofirmed by both SIMS ad TOF-SIMS (Time of flight SIMS). Better mass resolutio ca be obtaied by TOF-SIMS. Accordig to the SIMS aalysis for sample (EV75) i Fig. 7, 57 Fe/ 56 Fe was estimated at 1.8; very high value compared with the atural abudace of TOF-SIMS aalysis gave for 57 Fe/ 56 Fe as show i Fig. 7. Aomalous large 57 Fe/ 56 Fe was obtaied o a multi-layer sample (EV75) by both SIMS ad TOF-SIMS, though 57 Fe/ 56 Fe did ot agree with each other. The reaso is cosidered that 57 Fe/ 56 Fe deped o the aalyzed positio o the sample. Variatio of isotope ratio depedig o the locatio of aalysis are ofte observed[1]. As excess heat icreased, the amout of uclear products icreased. Figure 8 shows a example of Si powder product. I this case, large excess heat more tha iput power was obtaied. The powder is SiO, because Si was oxidized by O i the air after beig take out of the experimetal apparatus. The amouts of the Si reach 0.057g. I order to evaluate Si cotamiatio, we made a list of cadidates of cotamiatio source; solutio, multi-layer Pd, Pt aode, Ni coolig pipe, Polypropylee ad Teflo i the experimetal apparatus. The maximum quatity of Si cotamiats was estimated at 0.03g, which is smaller tha that of the obtaied Si powder. Fig. 8. Detected Si Powder Table. Isotope Ratio of Detected Si Powder Detected Si Powder Si Stadard Solutio Natural Isotope Itesity Isotope Ratio Itesity Isotope Ratio Abudace (cps) (%) (cps) (%) (%) 8 Si 4, , Si Si The isotope ratios of detected Si powder are show i Table. ICP-MS (Iductively Coupled Plasma Mass Spectrometry) was applied to the aalysis, the tabulated values were averaged by 5 times measuremets. Si of detected Si powder is smaller tha Si stadard solutio as show i the table. The isotopic compositio of Si powder detected i the apparatus after a experimet was differet from atural Si abudace. Judgig from the above results, the authors cosider that the detected Si powder is composed of uclear products ad Si impurities i the solutio. We should cofirm this result by performig the experimets with a improved solutio that cotais smaller amouts of Si.

8 REFFERENCES [1] Y. Iwamura, T. Itoh, N.Gotoh, M. Sakao, I. Toyoda ad H. Sakata, Detectio of Aomalous Elemets, X-ray ad Excess Heat Iduced by Cotiues Diffusio of Deuterium Through Multi-Layer Cathode (Pd/CaO/Pd), Proc. of ICCF-7, Vacouver, Caada, April 19-4, 1997, p. 167 [] Y. Iwamura, N. Gotoh, T. Itoh ad I. Toyoda, Detectio of Aomalous Elemets, X- ray ad Excess Heat i a D -Pd System ad its Iterpretatio by the Electro-Iduced Nuclear Reactio Model, Fusio Techology, vol. 33, No. 4, p. 476, 1998