Observation and analysis of time-dependent closed orbit motion in the LAMPF Proton Storage Ring

When the stored beam is artificially offset in a section of the LAMPF Proton Storage Ring by changing selected ring dipole strengths, there is evidence for a small time dependence of the offset during the course of beam injection. A complete discussion of the time dependence of orbit offsets should take into account at least the following possibilities: (1) correlations between the injection timing pattern and ring dipole field ripple, (2) correlations between the injection timing pattern and changes of beam position monitor characteristics, and (3) growth of space-charge effects as the number of stored protons increases. Since there is no a priori reason to expect the correlations mentioned, we have analyzed the observed time dependence of the beam offset in terms of space-charge effects only, although the other possible causes cannot be ruled out. The buildup of circulating charge during proton injection leads to a shift of the betatron tune of individual protons because of space-charge forces; this shift can cause a change of the individual proton closed-orbit positions, and consequently a change in the position of the beam as a whole. At the end of a PSR injection cycle there are approximately 2.5 {times} 10{sup 13} protons stored in the ring. The observed time dependence of the beam offset indicates a horizontal-plane tune shift of {minus}0.03 {plus minus} 0.02; this is consistent with a theoretical estimate of a maximum expected space-charge tune shift of {minus}0.09 when 2.5 {times} 10{sup 13} protons are stored in the ring. 3 refs., 4 figs

Immune Checkpoint Inhibitors Targeting the PD-1/PD-L1 Pathway in Advanced, Recurrent Endometrial Cancer: A Scoping Review with SWOT Analysis

Results of recent clinical trials using the immune check point inhibitors (ICI) pembrolizumab or dostarlimab with/without lenvatinib has led to their approval for specific molecular subgroups of advanced recurrent endometrial cancer (EC). Herein, we summarise the clinical data leading to this first tissue-agnostic approval. As this novel therapy is not yet available in the United Kingdom standard care setting, we explore the strengths, weaknesses, opportunities, and threats (SWOT) of ICI treatment in EC. Major databases were searched focusing on clinical trials using programmed cell death protein 1 (PD-1) and its ligand (PD-L1) ICI which ultimately contributed to anti-PD-1 approval in EC. We performed a data quality assessment, reviewing survival and safety analysis. We included 15 studies involving 1609 EC patients: 458 with mismatch repair deficiency (MMRd)/microsatellite instability-high (MSI-H) status and 1084 with mismatch repair proficiency/microsatellite stable (MMRp/MSS) status. Pembrolizumab/dostarlimab have been approved for MMRd ECs, with the addition of lenvatinib for MMRp cases in the recurrent setting. Future efforts will focus on the pathological assessment of biomarkers to determine molecular phenotypes that correlate with response or resistance to ICI in order to identify patients most likely to benefit from this treatment

Theoretical study of H sup minus stripping with a wiggler magnet

The first step for injecting protons into the LAMPF Proton Storage Ring (PSR) at LANL is to strip a beam of 800-MeV H{sup {minus}} ions to H{sup 0} with a 1.8-T dipole magnet. Because of the finite lifetime of energetic H{sup {minus}} ions in the magnetic field, their trajectories bend before stripping causing the angular spread of the beam, and therefore its emittance, to grow during the stripping process. In the case of the PSR, the horizontal beam emittance grows by a factor of roughly three during injection. As a consequence, beam losses in the ring are significantly greater than they would be if there were not emittance growth. A speculative technique is proposed in which the beam divergence growth and resulting emittance growth is reduced by stripping the H{sup {minus}} in a wiggler magnet whose transverse field alternates in direction as a function of position along the beam axis. The wiggler field configuration is adjusted so that the angular beam spread introduced during passage through one unidirectional-field increment of path is relatively small and so that 99.99% of the beam is stripped after passing through the whole magnet. With careful field design the net added angular beam spread is reduced because the incremental angular spreads are painted back and forth over the same small range. In the hypothetical case described, the calculated emittance growth and beam loss increase are significantly smaller than those calculated for a conventional stripper magnet. 3 refs., 3 figs

Analysis ob beam losses at PSR (Proton Storage Ring)

Beam losses and the resulting component activation at the Los Alamos Proton Storage Ring (PSR) have limited operating currents to about 30..mu..A average at a repetition rate of 15 Hz. Loss rates were found to be approximately proportional to the circulating current and can be understood by a detailed accounting of emittance growth in the two step injection process along with Coulomb scattering of the stored beam during multiple traversals of the injection foil. Calculations and simulations of the losses are in reasonable agreement with measurements

Experimental evidence for a Mott-Wigner glass phase of magnetite above the Verwey temperature

New muon-spin-relaxation (µSR) results on magnetite are reported and discussed in light of earlier Mössbauer, neutron, and µSR results. Modification of the µSR anomaly (observed at 247 K in zero field), when an external magnetic field is applied, provides evidence that the anomaly results from cross relaxation between the muon Larmor precession and the electron-correlation process in the B sublattice. The combined results strongly indicate that phonon-assisted electron hopping is the principal conduction mechanism above the Verwey transition temperature (TV). Together with theoretical evidence, these data support Mott’s suggestion that above TV magnetite is in the Wigner-glass state

A μSR study of valence fluctuations in Fe3O4

New µSR measurements on Fe3O4, showing a temperature shift of the "247 K anomaly" in applied fields, demonstrate muon-conduction-electron cross-relaxation and yield a 0.11 eV barrier for near-neighbor B-site electron transfer above the Verwey transition. µSR relaxation rates and the possibility of molecular-polaron formation are discussed