A large part of the material presented in this thesis will appear in two papers, • Cross-section of stopping n. Possible sources of error are considered and the accuracy of the measurements is assessed. An attachment port 20 inches from the bottom allows the top to be removed. with two winches.
The roller itself is mounted on a yoke which allows continuous adjustment of the tension in the belt. Because of the relatively large current drawn by the ion source focusing electrodes (Fig. 2), the power supplies are well filtered to reduce ripple to less than 100 volts. Therefore, less than a quarter of the total beam. from the probe can be focused with these energies.
A certain amount of regeneration of the cathodes could be achieved by injecting air. In the test chamber, a similar effect was noticed in that the core of the arc ~. An important function of the heated cathode appears to be that it keeps itself clean.
The windows in the corner distribution room were 1/8•. The relative window size at. each of the ten angles, 80° to 170°, was checked with a ThC' source at the target position.
III-21)
III-23) Rapid comparison over a very wide range of proton energy was made
D-D CROSS SECTION AND ANGULAR DISTRIBUTION 1. Spectrometer Observations
From the observed conditions and the kinetics of the reaction, the angular distribution at the center of mass of 8.1Stem was obtained. This is sufficient to obtain the total distribution due to the required eymmetry of the reaction in center-of-mass coordinates • The angular distribution was then expanded in Legendre polJnomials. Due to the large energy dependence of the reaction cross section at low energies, it was not possible to U88 thin ice targets at energies below about 200 kev.
The second method uses the excitation function at ~ = 1$0° and the angular distribution of the thin target, while the third plot is obtained from the integral over all angles of the differential cross section obtained by differentiating the gain of the thick target at each angle. The reaction yield is negligible below 400 kev • Cross sections obtained from the graphs shown in Fig. Correction D(dp); cross section (Fig. 14) was made assuming that for the reaction ol6(dp)o17•.
The procedure of extrapolating the trailing edge of the observed spectrometer spectrum to obtain Hmx has been justified as follows. The trailing edge in each cue is seen to be quite close to ~· Experi-. A comparison of the reaction yields from the monatomic, diatomic and triatomic ions indicated that radiation contamination was low.
Measurement of neutralization at lower energies was not feasible due to the relatively low yield. For the sparse target angle distribution data, the statistical uncertainty of the yield at each angle is less than 4% at each energy. An estimate of the uncertainties can be obtained from a comparison of the angular distribution and cross-sectional area obtained using both thin and thick target techniques.
The deviation from the sero experimental values for the term P6 (cosQ) in the angular distribution is considered an indicator of the experimental reliability of the method. Since the experiment measures the ratio of the reaction cross section to the stopping cross section, E, the uncertainties in the measurements of 6 described in the paper do not appear in "T (DD). In fact, the spectrometer effectively measured the ratio of the D(dp)H3 cross section to the al6 scattering cross section (pp)ol6.
Assigning a probable error to the experimental values is difficult because of the large number of uncertain factors that the expert has to deal with. The values of the total cross-section given in Table IV-3 are assigned 5%.
THEORETICAL CONSIDERATIONS 1. Ql6(pp)ol6 Cross Section
This is in reasonable agreement with the value for an effective radius of the Fermi-homas atom, a = 0.885 aor (z2)1/3. Equation {V-1) can now be integrated directly. This seems to confirm the assumption that the shape of the potential resulting from the electronic cloud is not important. X 'the partial wave 1 where the total angular momentum of the system is J = ( i + ! ) • Because the Coulomb barrier factor will tend to favor it.
Fitting experimental data on the location of the s1;2 resonances in F17 and its mirror nucleus, ol7, and the value of the scattering cross section oJ.6(nn)ol6 to thermal energies, R. G. Thomas<60) has estimated f over the range energy of interest, using a nuclear radius a= 5.27 x 1o-lJ em. Attempts to fit the experimental results in the D-D reaction to a relatively simple model of the nuclear interaction have been successful in accounting for the general behavior of the cross section and the angular distribution with energy. Although the experimental uncertainties in the work considered by Konopinski and TellerOO) are quite large, while Beiduk, et al.
It was impossible to match the eJq>erimental results without introducing significant spin-orbit coupling into the nuclear interaction. In the present work, a wide energy range was covered and the experimental uncertainties are considered low. The absence of resonances is implied by the smooth variation with energy of the angular distribution and the overall cross-section.
The increase of the asymmetry with energy implies that the higher partial waves must be considered according to their ability to penetrate the Coulomb barrier. Since the deuteron is a Bose particle, the total wave function must be symmetric with respect to an exchange of the particles, and. The energy release of the reaction is high enough (~4 llev) to allow orbitals up to the F-wave in the final state without needing it.
At low energies the fit of the angular coefficients is not bad and is within experimental uncertainties. 2j2 • The effect of the D wave on the angular distribution arises largely from the S-D interference term for which the barrier factor (P oP2)l/2 behaves approximately the same as PJ. However, conclusions based on the results obtained with such a simple model of the interaction must be conservative.
A better representation can probably be obtained by calculating the response width from the Coulomb wave function tables of Brey, et al., following the procedure of Christy and Latter (62). Although the complications introduced by the Coulomb field would add considerably to the numerical problems, it is to be hoped that the problem can be attacked by clearly introducing information about the internal structure of the deuteron.
