Kaplan, Selig

Paulikas, George A.

Pyle, Robert V.

eScholarship - University of California

Lawrence Berkeley National LaboratoryRecent WorkTitleDISSOCIATION OF H2+ IONS BY A MAGNETIC FIELDPermalinkhttps://escholarship.org/uc/item/6n39n3vjAuthorsKaplan, SeligPaulikas, George A.Pyle, Robert V.Publication Date1961-06-26eScholarship.org Powered by the California Digital LibraryUniversity of CaliforniaUCRL9763 UNIVERSITY OF CALIFORNIA er 	JaU'reMce lzml 0  0on TWO-WEEK LOAN COPY This is a LIbrary Circulating Copy whIch may be borrowed for two weeks. For a personal retention copy, call Tech. Info. DiuIsIon, Ext. 5545 BERKELEY, CALIFORNIA DISCLAIMER This document was prepared as an account of work sponsored by the United States Government. While this document is believed to contain correct information, neither the United States Government nor any agency thereof, nor the Regents of the University of California, nor any of their employees, makes any warranty, express or implied, or assumes any legal responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by its trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof, or the Regents of the University of California. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof or the Regents of the University of California. To be szbznittod to ?hyslcal Review Letters UCRL- 9763 UNIVERSITY Of CALIFORNIA. Lawrence Radiation Laboratory 8erkeiey, Ca1iornLa contract No. W-7405.erig48 DISSOCIATION OF 	IONS BY A MAGNETIC FIELD Selig Kaplan, Ceoz'ge A. PauliIae, and Robert V. Pyle June 26, 1961 I 2.. 	 UCRL-9763 DXSOCIATION OF H IONS BY A MAGNT!C FIELD ° Solig Kaplan4 George A. Pauflkas, and Robert V. Pyle Lawrence Radiation Laboratory University of California Berkeley, CaUfornia June 26, 1961 The dissociation of molecular ions by an externally applied electrtc field. E. or an equivalent eiectrlc field. E =.v x B. due to motion through a magnetic field has been calculated by Hiskea. Qualitatively, it is predicted that the external fields warp the nuclear potential in such a way that the higher vibrational states become unstable and dissociation results. This effect has be en observed recently by Rivierio. and Sweetman, who dissociated Hz and K ions of approximately 2 Mev energy with electric fieldi of up to 5X10 5 v/cm. The measurements presented here demonstrate the breakup of molecular hydrogen ions of 10 Mev per nucleon by static magnetic fields. The. experimental arrangement is shown in Fig. 1. Ions produced in a PIG discharge were accelerated in the 8erkeley heavy4eñ linear accelerator (Hilac). H2 + and .}i ions were continuously accelerated to full energy, and, alternatively, Lull-energy H ions were obtained by partially stripping 3..Mev H3 ions in a jet of Hg vapor and then accelerating the resulting H ions to 20 Mev. The reason for producing H by the latter technique is that such lone might be left In more highly excited àtates than those which came directly from the ion source as demonstrated by Riviere and Sweetman. The ions emerged from the Hilac accompanied by other particles formed by break-up on the residual gas in the vacuum system. The beam was collimated to 3/16X3/I6 in. • and the various particles were then separated by bending the useful beam by 15 deg in a dc magnetic fIeld. No further coUlmation was requl red. thuo eliminating background Lrom-up at slit edges. -3- 	 UCRL-9743 The dissociation and analysis were obtained In a dc magnet with a 4-in, gap. The gap in the first 1.5 In. of the tnagnet could be reduced to I in. thereby producing a maximum nagnet field of about 19 Itilogause. The beam reuired about 10 second to traverse this region. The results reported here were obtained by activating 0.010-in. -thick Cu foils, placed in the analyzing magnet perpendicular to the direction of the incident beam. The foil bolder was built t6 serve as a Faraday cup. and was used in the beam-monitoring system. The spatial distribution and the relative intensities of the beam particles (I. e., H° , H1 4 , H24' 0 etc.) were determined by counting the Zn63 activity (T 1 12 = 38 ruin) produced in the foil. Briefly, the scanning was done as follows: the bombarded Cu foil was '.rpped around a rotating wheel whose instantaneous position was synchronized with the voltage of a linear ramp. A Na! crystal viewed the wheel through a slit in a W and Pb shield. Whenever a 0.51-May anbThlation cy ray from Zn 3 decay was detected in the crystal, a pulse of height equal to the ramp voltage was generated. These pulses were put into a Penço 100-channel pulse-height analyzer, and a presentation of count rate vs position on the foil was obtained. The dissocIation caused by the residual gas In the vaCuum cyatem at our base pressure of about 6X10 6 mm Hg was determined by raising the pressure in several steps by adding N, measuring the dissociation, and extrapolating to the base preasuo. The H 4 ions obtained by stripping H3 were partially dissociated by the magnetic field, with a rapid rise at about 12 kilogauss. This magnetic field cor-responds to approximately 5x10 5 v/cm (FIg. 2). Our result is consistent with the - dissociation of the V = 17 vibrational state as calculated by I-iickes Lor nozirotating molecules. The vertical bands marked 	eec and' io14  see indicate the calculated -4- 	 UCRL-9763 fields necessary for barrier penetration in these times, with the widths of the bands corresponding to the uncertainties. The field in the 15-dég bending magnet was sufficiently high to have already dissociated the v = 18 vibrational state if it were populated.. Conversely, the maximum stripping field was somewhat too low to affect the v, 16 state.. 	 . No indication of magnetic field diseociatton was oalned for the directly accelerated H and H3 tone. We have no theoretical information concerning the H3 ion. The absence of dissociation of directly accelerated H 2 Who is assumed to be due to the method of formation and to possible de-excitation in the ion source. With more suitable choices of the kind of ion, energy ; and magnetic field strength, dissociation by a magnetic field might provide a mechanieth for trapping ions in a highly evacuated controlled thermonuclear device, and provide a diagnostic tool for the study of molecular tori formation and excitation. We are extending this investigation to other molecular tons and to neutral atoms in s$milar and higher magnotic fields. We wish to exprees our appreciation to Dr. C. M. Van Atta for supporting and encouraging this reéearch, J. Warren Stearna and Henry F. Rugge for helping with the measurements,, Dr. Edward L. Hubbard, Duane A. Speuce. and other members of the Hilac staff, for their aseistance, John R. Meneghetti for much of the mechanical construction, and Dr. John R. Hiske8 for many interesting and Qsemul theoretical discussions. One of the authors (S. j4.)  would like to thank Professor Burton J. Moyer for the support and interest that enabled him to participate in this work. -5- 	 UCRL-9763 Notes and Reference€ *WOrk done under the auspices of the U. S. _Atoiftic Energy Coznffiiseion. J. R. 	.skes. Phys. Rev. IZZe 1207 (1961). A. C. Riviere andD. .R. Sweetrnan, Phys. Rev. Letters 5, 560 (1960). gre. Captions Fig. 1.. Eperlmeuta1 arrangement. Fig. 2, FractIon of the beam dieociated by rnagnetic fields (preeent exerirnent) and electric field? (Rviere and weetman). L, magnetic, H' from 1 3 . magnetic, !7 direct; A. e1ectrlc, H from Ho electric, W' direct A background-gas break-np corresponding to a fraétional die.- soclation of (0.26d.04)Xi0' 3 has been substracted from the magnetic dssoclation data. The standard deviationo shown IncLude counting statistics, an estimated uncertainty of 15% in the extiápolatod dissociation by the residual gas in the vacuum cystem, and an wicertainty of 5 17a In the calibrations of foil activlty.vs. ion current. C, • I/I , II , 	I 4- a) 	 • 	a) CCY,  a •_a) a) 0. 00 I a)!.. • 	I-cl  LO —o a) a) 01 4x10 3 -a a) 3xlO a) - 4- - 	- 3 -o 2x.IO 1) I- a C) 0 U) U) -a E'. a IxtO a) 0 C 0 4- C) a LL. 0 o 	4 	5 	lz 	lb 	ZUIthogauss IL I 	 I i I I i .1 	 I 0 	200 400 	600 	800 ky/cm a 

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DISSOCIATION OF H2+ IONS BY A MAGNETIC FIELD

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DISSOCIATION OF H2+ IONS BY A MAGNETIC FIELD

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