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Two recent studies of the evolution of the isoscalar giant monopole resonance (ISGMR) within the calcium isotope chain report conflicting results. One study suggests that the monopole resonance energy, and thus the incompressibility of the nucleus $K_{A}$ increase with mass, which implies that $K_{\tau}$, the asymmetry term in the nuclear incompressibility, has a positive value. The other study reports a weak decreasing trend of the energy moments, resulting in a generally accepted negative value for $K_{\tau}$. An independent measurement of the central region of the ISGMR in the Ca isotope chain is provided to gain a better understanding of the origin of possible systematic trends. Inelastically scattered $\alpha$ particles from a range of calcium targets ($\mathrm{^{40,42,44,48}Ca}$), observed at small scattering angles including 0$^\circ$, were momentum analyzed in the K600 magnetic spectrometer at iThemba LABS, South Africa. Monopole strengths spanning an excitation-energy range between 9.5 and 25.5 MeV were obtained using the difference-of-spectra (DoS) technique. The structure of the $E0$ strength distributions of $^{40,42,44}$Ca agrees well with the results from the previous measurement that supports a weak decreasing trend of the energy moments, while no two datasets agree in the case of $^{48}$Ca. Despite the variation in the structural character of $E0$ strength distribution from different studies, we find for all datasets that the moment ratios, calculated from the ISGMR strength in the excitation-energy range that defines the main resonance region, display at best only a weak systematic sensitivity to a mass increase. Different trends observed in the nuclear incompressibility are caused by contributions to the $E0$ strength outside of the main resonance region, and in particular for high excitation energies., Comment: 11 pages, 11 figures, submitted to Physical Review C

Carbon burning is a key step in the evolution of massive stars, Type 1a supernovae and superbursts in x-ray binary systems. Determining the ^{12}C+^{12}C fusion cross section at relevant energies by extrapolation of direct measurements is challenging due to resonances at and below the Coulomb barrier. A study of the ^{24}Mg(α,α^{'})^{24}Mg reaction has identified several 0^{+} states in ^{24}Mg, close to the ^{12}C+^{12}C threshold, which predominantly decay to ^{20}Ne(ground state)+α. These states were not observed in ^{20}Ne(α,α_{0})^{20}Ne resonance scattering suggesting that they may have a dominant ^{12}C+^{12}C cluster structure. Given the very low angular momentum associated with sub-barrier fusion, these states may play a decisive role in ^{12}C+^{12}C fusion in analogy to the Hoyle state in helium burning. We present estimates of updated ^{12}C+^{12}C fusion reaction rates.

Background: Nuclei in the $sd$ shell demonstrate a remarkable interplay of cluster and mean-field phenomena. The $N=Z$ nuclei, such as $^{24}\mathrm{Mg}$ and $^{28}\mathrm{Si}$, have been the focus of the theoretical study of both phenomena in the past. A variety of different cluster structures in these nuclei are predicted, characterized by isoscalar dipole and monopole transitions. For example, low-energy isoscalar vortical dipole states were predicted in $^{24}\mathrm{Mg}$. The cluster and vortical mean-field phenomena can be probed by excitation of isoscalar monopole and dipole states in scattering of isoscalar particles such as deuterons or $\ensuremath{\alpha}$ particles.Purpose: We investigate, both experimentally and theoretically, the isoscalar dipole $IS1$ and monopole $IS0$ strengths in three essentially different light nuclei with different properties: stiff prolate $^{24}\mathrm{Mg}$, soft prolate $^{26}\mathrm{Mg}$, and soft oblate $^{28}\mathrm{Si}$. We analyze possible manifestations of clustering and vorticity in these nuclei.Methods: Inelastically scattered $\ensuremath{\alpha}$ particles were momentum analyzed in the K600 magnetic spectrometer at iThemba LABS, Cape Town, South Africa. The scattered particles were detected in two multiwire drift chambers and two plastic scintillators placed at the focal plane of the K600. In the theoretical discussion, the Skyrme quasiparticle random-phase approximation (QRPA) and antisymmetrized molecular dynamics $+$ generator coordinate method ($\mathrm{AMD}+\mathrm{GCM}$) were used.Results: A number of isoscalar monopole and dipole transitions were observed in the nuclei studied. Using this information, suggested structural assignments have been made for the various excited states. $IS1$ and $IS0$ strengths obtained within QRPA and $\mathrm{AMD}+\mathrm{GCM}$ are compared with the experimental data. The QRPA calculations lead us to conclude that (i) the mean-field vorticity appears mainly in dipole states with $K=1$, (ii) the dipole (monopole) states should have strong deformation-induced octupole (quadrupole) admixtures, and (iii) near the $\ensuremath{\alpha}$-particle threshold there should exist a collective state with $K=0$ for prolate nuclei and $K=1$ for oblate nuclei, with an impressive octupole strength. The results of the $\mathrm{AMD}+\mathrm{GCM}$ calculations suggest that some observed states may have a mixed (mean-field $+$ cluster) character or correspond to particular cluster configurations.Conclusion: A tentative correspondence between observed states and theoretical states from QRPA and $\mathrm{AMD}+\mathrm{GCM}$ was established. The QRPA and $\mathrm{AMD}+\mathrm{GCM}$ analysis shows that low-energy isoscalar dipole states combine cluster and mean-field properties. The QRPA calculations show that the low-energy vorticity is well localized in $^{24}\mathrm{Mg}$, fragmented in $^{26}\mathrm{Mg}$, and absent in $^{28}\mathrm{Si}$.

Background: Inelastic proton scattering at energies of a few hundred MeV and very-forward angles including $0^\circ$ has been established as a tool to study electric-dipole strength distributions in nuclei. The present work reports a systematic investigation of the chain of stable even-mass Nd isotopes representing a transition from spherical to quadrupole-deformed nuclei. Purpose: Extraction of the equivalent photo-absorption cross sections and analysis of their fine structure in the energy region of the IsoVector Giant Dipole Resonance (IVGDR). Method: Proton inelastic scattering reactions of 200 MeV protons were measured at iThemba LABS in Cape Town, South Africa. The scattering products were momentum-analysed by the K600 magnetic spectrometer positioned at $\theta_{\mathrm{Lab}}=0^\circ$. Using dispersion-matching techniques, energy resolutions of $\Delta E \approx 40 - 50$ keV were obtained. After subtraction of background and contributions from other multipoles, the spectra were converted to photo-absorption cross sections using the equivalent virtual-photon method. Results: Wavelet-analysis techniques are used to extract characteristic energy scales of the fine structure of the IVGDR from the experimental data. Comparisons with the Quasiparticle-Phonon Model (QPM) and Skyrme Separable Random Phase Approximation (SSRPA) predictions provide insight into the role of different giant resonance damping mechanisms. Conclusions: Fine structure is observed even for the most deformed nuclei studied. Fragmentation of the one particle-one hole ($1p1h$) strength seems to be the main source of fine structure in both spherical and deformed nuclei. Some impact of the spreading due to coupling of the two particle-two hole ($2p2h$) states to the $1p1h$ doorway states is seen in the spherical/transitional nuclei, where calculations beyond the $1p1h$ level are available.

The isobaric nuclei 20Ne and 20F were investigated with the 22Ne(p,t)20Ne and 22Ne(p,3He)20F reactions using a beam of protons at Ep = 80 MeV. The former reaction was employed to confirm a tentative candidate for the 5-alpha cluster state in 20Ne, while the latter was used to look for T = 2 isobaric analogue partner states in 20F to states which were already observed above Ex = 20 MeV in 20Ne. The existence of a state which could be considered as a candidate for the 5-alpha cluster state is confirmed here as well as the T = 2 IAS states in 20Ne.

CITATION: Mukwevho, N. J., et al. 2018. Second T = 3/2 state in 9B and the isobaric multiplet mass equation. Physical Review C, 98(5):051302, doi:10.1103/PhysRevC.98.051302.

The development and verification of the Single-Event-Effect (SEE) Proton Testing of electronic systems facility at iThemba LABS using a novel Beam Loss Monitor (BLM) based dosimetry system is presented. This is the first high-energy proton SEE testing facility in Africa and the Southern hemisphere.

Background: The Ne-22(alpha, n)Mg-25 reaction is an important source of neutrons for the s-process. Direct measurement of this reaction and the competing Ne-22(alpha,gamma)Mg-26 reaction are challenging due to the gaseous nature of both reactants, the low cross section and the experimental challenges of detecting neutrons and high-energy gamma rays. Detailed knowledge of the resonance properties enables the rates to be constrained for s-process models. Purpose: Previous experimental studies have demonstrated a lack of agreement in both the number and excitation energy of levels in Mg-26. To try to resolve the disagreement between different experiments, proton and deuteron inelastic scattering from Mg-26 have been used to identify excited states. Method: Proton and deuteron beams from the tandem accelerator at theMaier-Leibnitz Laboratorium at Garching, Munich, were incident upon enriched (MgO)-Mg-26 targets. Scattered particles were momentum-analyzed in the Q3D magnetic spectrograph and detected at the focal plane. Results: Reassignments of states around E-x = 10.8-10.83 MeV in Mg-26 suggested in previous works have been confirmed. In addition, new states in Mg-26 have been observed, two below and two above the neutron threshold. Up to six additional states above the neutron threshold may have been observed compared to experimental studies of neutron reactions on Mg-25, but some or all of these states may be due to Mg-24 contamination in the target. Finally, inconsistencies between measured resonance strengths and some previously accepted J(pi) assignments of excited Mg-26 states have been noted. Conclusion: There are still a large number of nuclear properties in Mg-26 that have yet to be determined and levels that are, at present, not included in calculations of the reaction rates. In addition, some inconsistencies between existing nuclear data exist that must be resolved in order for the reaction rates to be properly calculated.

A survey of the fine structure of the Isovector Giant Dipole Resonance (IVGDR) was performed, using the recently commissioned zero-degree facility of the K600 magnetic spectrometer at iThemba LABS. Inelastic proton scattering at an incident energy of 200 MeV was measured on $^{27}$Al, $^{40}$Ca, $^{56}$Fe, $^{58}$Ni and $^{208}$Pb. A high energy resolution ($\rm{\Delta}\it{E} \simeq$ 40 keV FWHM) could be achieved after utilising faint-beam and dispersion-matching techniques. Considerable fine structure is observed in the energy region of the IVGDR and characteristic energy scales are extracted from the experimental data by means of a wavelet analysis. The comparison with Quasiparticle-Phonon Model (QPM) calculations provides insight into the relevance of different giant resonance decay mechanisms. Photoabsorption cross sections derived from the data assuming dominance of relativistic Coulomb excitation are in fair agreement with previous work using real photons., Comment: 15 pages, 15 figures

A number of nuclear physics experiments at iThemba LABS require target foils that consist of specific isotopes of elements which are reactive in air. Not only is it important to prepare these targets in a suitable environment to prevent oxidation, but consideration should also be given to the long term storage and handling facilities of such targets. The target vacuum storage facility at iThemba LABS, as well as additional hardware necessary to transport and install the target foils in the experimental chamber, will be discussed.

Background: The $^{22}\mathrm{Ne}$($\ensuremath{\alpha},n$)$^{25}\mathrm{Mg}$ reaction is one of the neutron sources for the $s$ process in massive stars. The properties of levels in $^{26}\mathrm{Mg}$ above the $\ensuremath{\alpha}$-particle threshold control the strengths of the $^{22}\mathrm{Ne}$($\ensuremath{\alpha},n$)$^{25}\mathrm{Mg}$ and $^{22}\mathrm{Ne}$($\ensuremath{\alpha},\ensuremath{\gamma}$)$^{26}\mathrm{Mg}$ reactions. The strengths of these reactions as functions of temperature are one of the major uncertainties in the $s$ process.Purpose: Information on the existence, spin, and parity of levels in $^{26}\mathrm{Mg}$ can assist in constraining the strengths of the $^{22}\mathrm{Ne}$($\ensuremath{\alpha},\ensuremath{\gamma}$)$^{26}\mathrm{Mg}$ and $^{22}\mathrm{Ne}$($\ensuremath{\alpha},n$)$^{25}\mathrm{Mg}$ reactions, and therefore in constraining $s$-process abundances.Methods: Inelastically scattered $\ensuremath{\alpha}$ particles from a $^{26}\mathrm{Mg}$ target were momentum-analyzed in the K600 magnetic spectrometer at iThemba LABS, South Africa. The differential cross sections of states were deduced from the focal-plane trajectory of the scattered $\ensuremath{\alpha}$ particles. Based on the differential cross sections, spin and parity assignments to states are made.Results: A newly assigned ${0}^{+}$ state was observed in addition to a number of other states, some of which can be associated with states observed in other experiments. Some of the deduced ${J}^{\ensuremath{\pi}}$ values of the states observed in the present study show discrepancies with those assigned in a similar experiment performed at RCNP Osaka. The reassignments and additions of the various states can strongly affect the reaction rate at low temperatures.Conclusion: The number, location, and assignment of levels in $^{26}\mathrm{Mg}$ that may contribute to the $^{22}\mathrm{Ne}+\ensuremath{\alpha}$ reactions are not clear. Future experimental investigations of $^{26}\mathrm{Mg}$ must have an extremely good energy resolution to separate the contributions from different levels. Coincidence experiments of $^{26}\mathrm{Mg}$ provide a possible route for future investigations.

International audience; The theoretical and experimental determination of superdeformed states in nuclei in the mass region A≤40 has been since a long time one of the major challenges of nuclear structure studies. Despite the considerable experimental and theoretical work dedicated to this topic, up to now superdeformed bands have been found in only two nuclei, $^{36}$Ar and $^{40}$Ca. While the experimental signature of the superdeformed nature of those states is irrefutable, their theoretical interpretation is still uncertain. In particular, it is not clear whether clusterisation is responsible of the onset of superdeformation. For this reason, we wanted to investigate an even lighter system, $^{28}$Si, where a number of theoretical calculations predict the presence of superdeformation as an effect of the cluster structure of the nucleus.

The phenomenon of fine structure of the Isoscalar Giant Quadrupole Resonance (ISGQR) has been studied with high energy-resolution proton inelastic scattering at iThemba LABS in the chain of stable even-mass Nd isotopes covering the transition from spherical to deformed ground states. A wavelet analysis of the background-subtracted spectra in the deformed 146,148,150Nd isotopes reveals characteristic scales in correspondence with scales obtained from a Skyrme RPA calculation using the SVmas10 parameterization. A semblance analysis shows that these scales arise from the energy shift between the main fragments of the K = 0, 1 and K = 2 components., 7 pages, 6 figures

CITATION: Long, A. M., et al. 2017. Indirect study of the stellar ³⁴ Ar(α,p) ³⁷K reaction rate through ⁴⁰Ca(p,t) ³⁸Ca reaction measurements. Physical Review C, 95(5):1-9, doi:10.1103/PhysRevC.95.055803.

A prominent candidate for a Hoyle-analogue state in 16O is the 0+ 6 state, previously observed at Ex = 15.097(5) MeV. This state is identified by several theoretical cluster calculations to be a good candidate for the 4-α cluster state, analogous to the Hoyle state in 12C. Whilst much theoretical work has been performed to reconcile a calculated α-cluster state with this resonance, the experimental information on this state remained very scarce. To investigate this state, the 16O(α, α') reaction was studied at θlab = 0° at an incident energy of Elab = 200 MeV using the K600 magnetic spectrometer at iThemba LABS. For the first time, the decay channels of the Ex = 15.097(5) MeV state were isolated using a large acceptance silicon-strip detector array at backward angles. The lineshapes of the states were analysed within a phenomenological R-matrix framework. Results indicate the presence of a resonance at Ex ≈ 15 MeV which does not exhibit a Jπ = 0+ nature.

The $^{16}\mathrm{O}(\ensuremath{\alpha},{\ensuremath{\alpha}}^{\ensuremath{'}})$ reaction was studied at ${\ensuremath{\theta}}_{\mathrm{lab}}={0}^{\ensuremath{\circ}}$ at an incident energy of ${E}_{\mathrm{lab}}=200$ MeV using the K600 magnetic spectrometer at iThemba LABS. Proton decay and $\ensuremath{\alpha}$ decay from the natural parity states were observed in a large-acceptance silicon strip detector array at backward angles. The coincident charged-particle measurements were used to characterize the decay channels of the ${0}_{6}^{+}$ state in $^{16}\mathrm{O}$ located at ${E}_{x}=15.097(5)$ MeV. This state is identified by several theoretical cluster calculations to be a good candidate for the $4\text{\ensuremath{-}}\ensuremath{\alpha}$ cluster state. The results of this work suggest the presence of a previously unidentified resonance at ${E}_{x}\ensuremath{\approx}15$ MeV that does not exhibit a ${0}^{+}$ character. This unresolved resonance may have contaminated previous observations of the ${0}_{6}^{+}$ state.

Background: Aspects of the nuclear structure of light α-conjugate nuclei have long been associated with nuclear clustering based on α particles and heavier α-conjugate systems such as C12 and O16. Such structures are associated with strong deformation corresponding to superdeformed or even hyperdeformed bands. Superdeformed bands have been identified in Ca40 and neighboring nuclei and find good description within shell model, mean-field, and α-cluster models. The utility of the α-cluster description may be probed further by extending such studies to more challenging cases comprising lighter α-conjugate nuclei such as Mg24, Si28, and S32. Purpose: The purpose of this study is to look for the number and energy of isoscalar 0+ states in Si28. These states are the potential bandheads for superdeformed bands in Si28 corresponding to the exotic structures of Si28. Of particular interest is locating the 0+ bandhead of the previously identified superdeformed band in Si28. Methods: α-particle inelastic scattering from a Sinat target at very forward angles including 0 has been performed at the iThemba Laboratory for Accelerator-Based Sciences in South Africa. Scattered particles corresponding to the excitation energy region of 6 to 14 MeV were momentum-analysed in the K600 magnetic spectrometer and detected at the focal plane using two multiwire drift chambers and two plastic scintillators. Results: Several 0+ states have been identified above 9 MeV in Si28. A newly identified 9.71 MeV 0+ state is a strong candidate for the bandhead of the previously discussed superdeformed band. The multichannel dynamical symmetry of the semimicroscopic algebraic model predicts the spectrum of the excited 0+ states. The theoretical prediction is in good agreement with the experimental finding, supporting the assignment of the 9.71-MeV state as the bandhead of a superdeformed band. Conclusion: Excited isoscalar 0+ states in Si28 have been identified. The number of states observed in the present experiment shows good agreement with the prediction of the multichannel dynamical symmetry.

The gamma strength function and level density of 1- states in 96Mo have been extracted from a high-resolution study of the (p,p') reaction at 295 MeV and extreme forward angles. By comparison with compound nucleus $\gamma$ decay experiments, this allows a test of the generalized Brink-Axel hypothesis in the energy region of the Pygmy Dipole Resonance. The Brink-Axel hypothesis is commonly assumed in astrophysical reaction network calculations and states that the gamma strength function in nuclei is independent of the structure of initial and final state. The present results validiate the Brink-Axel hypothesis for 96Mo and provide independent confirmation of the methods used to separate gamma strength function and level density in $\gamma$ decay experiments., Comment: 6 pages, 4 figures

The setup and experimental techniques for measurements of zero-degree inelastic scattering and reactions involving light ions with the K=600 magnetic spectrometer at iThemba LABS are described. Measurements were performed for inelastic proton scattering at an incident energy of 200 MeV for targets ranging from 27Al to 208Pb. An energy-resolution of 45 keV (FWHM) was achieved by utilizing the faint-beam dispersion-matching technique. A background subtraction procedure was applied and allowed for the extraction of excitation energy spectra with low background. Measurements of the (p,t) reaction at zero degrees for Ep=100 and 200 MeV benefited from the difference in magnetic rigidity between the reaction products and the beam particles, resulting in background-free spectra with an excitation energy-resolution of 32 and 48 keV (FWHM), respectively, and a scattering angle resolution of 0.55° (FWHM). The addition of Double Sided Silicon Strip Detectors (DSSSD) at backward scattering angles allowed for coincident measurements of particle-decay of states excited in the (p,t) reaction at E p = 200 MeV .

CITATION: Latif, M. B., et al. 2019. Evolution of the IVGDR and its fine structure from doubly-magic 40⁴°Ca to neutron-rich ⁴⁸Ca probed Using (p,p′) scattering. Acta Physica Polonica B, 50(3):461-468, doi:10.5506/APhysPolB.50.461.

Aspects of alpha-clustering in nuclei were studied at iThemba LABS over the past twenty years by means of quasi-free scattering, inelastic scattering and transfer reactions and through particle decay spectroscopy. An overview of relevant work is provided, which highlights the unique opportunities at iThemba LABS, specifically with the K600 zero degree facility and recently commissioned ancillary detection systems.

The structure of the nucleus C 12 is discussed, in particular the spectrum of states above the α-decay threshold. A search for the 2+ excitation of the Hoyle-state is reported. The structural link between halo-like states and molecular states is explored in the case of Be 11 .

Spherical silver nanoparticles were prepared by means of ion beam synthesis in lithium niobate. The embedded nanoparticles were then irradiated with energetic (84)Kr and (197)Au ions, resulting in different electronic energy losses between 8.1 and 27.5 keV nm(-1) in the top layer of the samples. Due to the high electronic energy losses of the irradiating ions, molten ion tracks are formed inside the lithium niobate in which the elongated Ag nanoparticles are formed. This process is strongly dependent on the initial particle size and leads to a broad aspect ratio distribution. Extinction spectra of the samples feature the extinction maximum with shoulders on either side. While the maximum is caused by numerous remaining spherical nanoparticles, the shoulders can be attributed to elongated particles. The latter could be verified by COMSOL simulations. The extinction spectra are thus a superposition of the spectra of all individual particles.

The combination of a magnetic spectrometer and ancillary detectors such as silicon detectors is a powerful tool for the study of nuclear reactions and nuclear structure. This paper discusses the recently commissioned silicon array called the CAKE which is designed for use with the K600 magnetic spectrometer at iThemba LABS., Comment: 9 figures, Journal of Instrumentation 12 (02), T02004

The electric dipole strength distribution in 120Sn between 5 and 22 MeV has been determined at RCNP Osaka from a polarization transfer analysis of proton inelastic scattering at E_0 = 295 MeV and forward angles including 0{\deg}. Combined with photoabsorption data an electric dipole polarizability \alpha_D(120Sn) = 8.93(36) fm^3 is extracted. The dipole polarizability as isovector observable par excellence carries direct information on the nuclear symmetry energy and its density dependence. The correlation of the new value with the well established \alpha_D(208Pb) serves as a test of its prediction by nuclear energy density functionals (EDFs). Models based on modern Skyrme interactions describe the data fairly well while most calculations based on relativistic Hamiltonians cannot., Comment: 6 pages, 4 figures

Differential cross sections of isoscalar and isovector spin-M1 (0(+)→1(+)) transitions are measured using high-energy-resolution proton inelastic scattering at E(p)=295 MeV on (24)Mg, (28)Si, (32)S, and (36)Ar at 0°-14°. The squared spin-M1 nuclear transition matrix elements are deduced from the measured differential cross sections by applying empirically determined unit cross sections based on the assumption of isospin symmetry. The ratios of the squared nuclear matrix elements accumulated up to E(x)=16 MeV compared to a shell-model prediction are 1.01(9) for isoscalar and 0.61(6) for isovector spin-M1 transitions, respectively. Thus, no quenching is observed for isoscalar spin-M1 transitions, while the matrix elements for isovector spin-M1 transitions are quenched by an amount comparable with the analogous Gamow-Teller transitions on those target nuclei.

The excited states of the $^{20}\mathrm{Ne}$ nucleus from the ground state to ${E}_{x}$ = 25 MeV were investigated with the $^{22}\mathrm{Ne}$($p,t$)$^{20}\mathrm{Ne}$ reaction at a beam energy of ${E}_{p}$ = 60 MeV using the QDD magnetic spectrometer at iThemba LABS. Narrow, low-spin ${J}^{\ensuremath{\pi}}={0}^{+},{1}^{\ensuremath{-}}$, and ${2}^{+}$ states have been observed for the first time at high-excitation energies in $^{20}\mathrm{Ne}$, namely at ${E}_{x}$ = 17.67, 18.84, 20.59, 21.16, 21.80, and 22.5 MeV. Shell-model and coupled reaction channel calculations were performed to determine the nature of the newly observed states. Candidates for $T$ = 2 states are proposed at 3.86(5), 4.43(5) MeV and 5.07(5) MeV above the lowest ${0}^{+},T$ = 2 state at ${E}_{x}\phantom{\rule{0.16em}{0ex}}=\phantom{\rule{0.16em}{0ex}}16.73$ MeV. Two of these $T$ = 2 candidates appear to result from core excitations in the $0p$ shell. The state at ${E}_{x}$ = 22.5 MeV, which could not be interpreted by the shell-model calculations, is a tentative candidate for the 5-$\ensuremath{\alpha}$ cluster state.

Spectra of inclusive double differential cross sections of 3 He and 6 He fragments produced in the interaction of 12 C with 93 Nb at 400 MeV are measured and analyzed. As was found for the production of intermediate mass fragments in this and similar reactions involving light projectiles, the spectra can to a large extent be satisfactorily reproduced only by considering the contribution of projectile break-up as well as nucleon coalescence.

A cryogenic horizontal single loop target has been designed, built, tested and operated for the G 0 experiment in Hall C at Jefferson Lab. The target cell is 20 cm long, the loop volume is 6.5 l and the target operates with the cryogenic pump fully immersed in the fluid. The target has been designed to operate at 30 Hz rotational pump speed with either liquid hydrogen or liquid deuterium. The high-power heat exchanger is able to remove 1000 W of heat from the liquid hydrogen, while the nominal electron beam with current of 40 μ A and energy of 3 GeV deposits about 320 W of heat into the liquid. The increase in the systematic uncertainty due to the liquid hydrogen target is negligible on the scale of a parity violation experiment. The global normalized yield reduction for 40 μ A beam is about 1.5% and the target density fluctuations contribute less than 238 ppm (parts per million) to the total asymmetry width, typically about 1200 ppm, in a Q 2 bin.

The electric dipole strength in 120Sn has been extracted from proton inelastic scattering experiments at E_p = 295 MeV and at forward angles including 0 degree. Below neutron threshoild it differs from the results of a 120Sn(gamma,gamma') experiment and peaks at an excitation energy of 8.3 MeV. The total strength corresponds to 2.3(2)% of the energy-weighted sum rule and is more than three times larger than what is observed with the (gamma,gamma') reaction. This implies a strong fragmentation of the E1 strength and/or small ground state branching ratios of the excited 1- states., 7 pages, 6 figures

Differential cross sections of isoscalar and isovector spin-M1 (0(+)→1(+)) transitions are measured using high-energy-resolution proton inelastic scattering at E(p)=295 MeV on (24)Mg, (28)Si, (32)S, and (36)Ar at 0°-14°. The squared spin-M1 nuclear transition matrix elements are deduced from the measured differential cross sections by applying empirically determined unit cross sections based on the assumption of isospin symmetry. The ratios of the squared nuclear matrix elements accumulated up to E(x)=16 MeV compared to a shell-model prediction are 1.01(9) for isoscalar and 0.61(6) for isovector spin-M1 transitions, respectively. Thus, no quenching is observed for isoscalar spin-M1 transitions, while the matrix elements for isovector spin-M1 transitions are quenched by an amount comparable with the analogous Gamow-Teller transitions on those target nuclei.