Alpha-Alpha Scattering in the Range 36.8 to 47.3 Mev

Abstract

Absolute cliffereuti.al c:roae sections for the elastic scattering of alpha particles floom helium have been obtained at 36.8, 38.8, 40.8, 41.9, 44.4, 4:6.1, 47.1, and 47.3 m cr<ler to provide a check on the eonaistency of the results, the data were taken at alternate angles in.•u.ch a way that eaeh angular distribution was taken at least twice. 1n addition, several points on each curve were remeasured one or more times to ensure that no electrical or mec:banieal drift was pree.ent in the apparatus. Sinee the scattering of identical partidee impoeea angtllar-distrihution symmetry with respect to 90 cleg. c. m., some check-points were taken at c. m. angles larger than 90 deg.Secoad·order geometry co&"rectiona to the c.reea sections were . . 10 made, baaed on the calclllation of .Critchfield and Dodder. , Theee corrections became ae la.rge as 35% at the narrow m~nima of. the angular distributiona. At other angles they were of the O&"der of r~ or less.The preaeure of the heiium gas ln the chamber waa measured with a mercury manometer, and the temperature was meaa\l:red with a tl:u~:rmometer in thermal contact with the chamber. Error•The charge-collecting system waa calibrated aaa1aat ~voltage and capacitive standards and waa eltimatecl to have an over-all accuracy oftt: o.so·% relative, and • a. 75% abaolute, for each croaa aeetion.The helium gaa ued in the scattering chamber waa supplied by Liquid Carbonic Co. from the V. S. Bureau of Mines 'bottling service at AmarUlo. Texas. and waa 1ped!led. to have less than 0.005% of impurity, mainly air and hydrogeu. Tb.ie amount was negligible. The measurement of temperature ancl prea1v.re of the helium gaa in the chamber was estimated --. to introduce an absolute error in the determination o£ the density of the helium gas varyina from • 0.3., to • l.0'1u. This depen4.ed mainly on the helium gaa preeaul'e for each rUD. and the percentage accuracy with which it could be determined.. At each aaale, tl\e energy apectr\lm wae obtained with sufflcient pointe above and below the peak corresponding to elastically scattered alpha particle• to eaable the background curve to be well determined. This curve waa then extrapolated into the el.astic peak, aad those coWltl arf.1ing from baekgrou.ad were .ab.btracted from the total c0'\11\tl in the peak. The background corl'ectlon was quite emall, and generally negUgible at the higher energies, except at uglea near mmima in the eroas section. Below 41.9Mev, however, the size of this bac'kgro~ncl correction became cG\siderably laraer, aad., consequently, at the lower energies the error associated with this backgrou.r&d correction accoun~e for moet of the tabulated relativ·e error on each eros s eectioo.At the low pressures of helium gaa in the chamber. the poasibUity of the loss of some beam from the Fal'aday cup by multiple scattering iu the gas wae negligible. and wae calculated to be lees than 0.11\ . UCRL-882?The errors listed in Table 1 are relative errors. The absolute errors were compounded separately and result in ...

Alpha–alpha potential up to 47.3 MeV bombarding energy

“…Experimental differential cross sections of elastic scattering data are available over the energy range of 150 keV to 650 MeV [1][2][3][4][5][6][7][8][9][10][11][12]. However, we have analyzed here the data up to 47.3 MeV only because the experimental total reaction cross sections increase substantially [2] at higher energies implying that the absorption plays a significant role.…”

“…The parameters V 0 and R 0 are applicable to the WS attractive real part while V A and R A , to the Gaussian attractive real one. V 0 , V A , V R and W 00 are in MeV; R 0 , R A , R R and a 0 , in fm; and J R /16 and J I /16, in MeV fm 3 parameter V R followed by an adjustment of other parameters including the depth of the attractive part, either V A in (9) or V 0 in (10). This is because the EDF potential parameters have been generated using the width parameter γ = 0.5, which does not adequately reproduce the correct central density of about ρ 0 = 0.32 fm −3 of α-particles, and thus, may not have generated enough strength for the repulsive core.…”

“…The α-α system has been studied quite extensively both experimentally [1][2][3][4][5][6][7][8][9][10][11][12] and theoretically . Ostensibly, the determination of the interaction potential for this system should be simple.…”

The4He(?,p)7Li,7Li*0.478 reaction near threshold

“…The variable-energy feature of the Berkeley 88 inch cyclotron was particularly useful for the present investigation, which overlaps older experiments carried out at the old Berkeley Crocker Laboratory [7], degrading the 48 MeV alpha particle beam energy with foils. The beam energy width for typical operating conditions was small (about 30 keV), permitting therefore small and meaningful steps for the measurement of the angular distributions with sufficient detail.…”

“…The beam energy width for typical operating conditions was small (about 30 keV), permitting therefore small and meaningful steps for the measurement of the angular distributions with sufficient detail. The advent of solid state detectors, with higher resolution (100 keV) and lower background than the crystals used in the Crocker Laboratory experiments [7], permitted the detection and perfect separation of protons from the transitions to the ground and first excited states of VLi, as shown in Fig. 1.…”