Search results for "Accelerator Physics"
showing 10 items of 1294 documents
Spin distribution measurement for 64Ni + 100Mo at near and above barrier energies
2015
Spin distribution measurements were performed for the reaction 64 Ni + 100 Mo at three beam energies ranging from 230 to 260 MeV. Compound nucleus (CN) spin distributions were obtained channel selective for each evaporation residue populated by the de-excitation cascade. A comparison of the spin distribution at different beam energies indicates that its slope becomes steeper and steeper with increasing beam energy. This change in slope of the spin distribution is mainly due to the onset of fission competition with particle evaporation at higher beam energies.
Hyperfine structure measurements of neutral niobium with Fourier transform spectroscopy
2010
Aims. We report on experimental studies of hyperfine structure splitting of neutral niobium.Methods. We used high-resolution Fourier transform spectroscopy to record a spectrum of niobium produced with a hollow cathode discharge lamp in the range of wavenumbers from 10 000 cm-1 to 30 000 cm-1 .Results. The magnetic dipole hyperfine structure constants A were determined for the 109 levels of odd parity by analyzing the profiles of 224 spectral lines. The A values of 57 of these level are reported for the first time.
Evidence of 200 TeV photons from HAWC J1825-134
2020
The Earth is bombarded by ultra-relativistic particles, known as cosmic rays (CRs). CRs with energies up to a few PeV (=10$^{15}$ eV), the knee in the particle spectrum, are believed to have a Galactic origin. One or more factories of PeV CRs, or PeVatrons, must thus be active within our Galaxy. The direct detection of PeV protons from their sources is not possible since they are deflected in the Galactic magnetic fields. Hundred TeV $\gamma$-rays from decaying $\pi^0$, produced when PeV CRs collide with the ambient gas, can provide the decisive evidence of proton acceleration up to the knee. Here we report the discovery by the High Altitude Water Cherenkov (HAWC) observatory of the $\gamma…
Field Fluctuations in a One-Dimensional Cavity with a Mobile Wall
2013
We consider a scalar field in a one-dimensional cavity with a mobile wall. The wall is assumed bounded by a harmonic potential and its mechanical degrees of freedom are treated quantum mechanically. The possible motion of the wall makes the cavity length variable, and yields a wall-field interaction and an effective interaction among the modes of the cavity. We consider the ground state of the coupled system and calculate the average number of virtual excitations of the cavity modes induced by the wall-field interaction, as well as the average value of the field energy density. We compare our results with analogous quantities for a cavity with fixed walls, and show a correction to the Casim…
Collinear laser spectroscopy of high-energy Li-like11B beam
1997
As part of the RIKEN RIBF (RI beam factory) program, high-resolution x-ray spectroscopy for highly-charged radioactive isotope beams, is proposed in order to make a systematic study of the mean-square nuclear charge radii and moments of short lived radioactive isotopes far from the line of stability. To examine the feasibility of the experiment, we are now performing a test experiment using a laser beam and Li-like ion beams from RIKEN ring cyclotron. The D1 resonance line of a 11B2+ beam was clearly observed for the first time.
Beam-based alignment of SRF cavities in an electron injector linac
2018
Proper alignment of accelerating cavities is an important issue concerning beam quality of linear rf-accelerators. In particular, SRF cavities of injector linacs using high accelerating gradients on low-velocity electron beams can deteriorate the beam quality significantly when not aligned sufficiently. On the other hand, knowing the exact position of every cavity after several cool-down cycles of a cryomodule can be difficult depending on the particular module design. We will report on operational experience on the SC injector of the Darmstadt superconducting recirculating linac and ERL (S-DALINAC) showing unwanted effects on beam dynamics and beam quality due to cavity misalignment, such…
Space charge and microbunching studies for the injection arc of MESA
2018
For intense electron bunches traversing through bends, as for example the recirculation arcs of an ERL, space charge (SC) may result in beam phase space deterioration. SC modifies the electron transverse dynamics in dispersive regions along the beam line and causes emittance growth for mismatched beams or for specific phase advances. On the other hand, longitudinal space charge together with dispersion can lead to the microbunching instability. The present study focuses on the 180° low energy (5 MeV) injection arc lattice for the multi-turn Mainz Energy-recovering Superconducting Accelerator (MESA), which should deliver a CW beam at 10⁵ MeV for physics experiments with an internal target. W…
Dark matter synchrotron emission and radio observations
2012
We compute the synchrotron emission induced by electrons produced by DM annihilations inside our galaxy. The signal is compared with observations in a large range of frequencies, from 22 MHz up to 1420 MHz. We set constraints on the DM mass and annihilation cross-section and highlight the impact of astrophysical uncertainties.
Compton transmission polarimeter for a very precise polarization measurement within a wide range of electron currents
2011
For new experiments with polarized electron and positron beams the precise and quick measurement of the beam polarization is required. The relative electron polarization has been monitored on-line using a compact transmission Compton polarimeter for a wide range of average electron currents up to 100/μA and electron beam energy of 3.5 MeV. The asymmetry induced by the beam polarization can be monitored precisely with ΔA/A < 0.2 %. Even small relative variations of the beam polarization during a beam time may be detected using this polarimeter, such as an increase ~ 1 % and subsequent decrease of the beam polarization.
The dynamics of bunched laser-cooled ion beams at relativistic energies
2007
We discuss the axial dynamics of laser-cooled relativistic C3+ ion beams at moderate bunching voltages. Schottky noise spectra measured at a beam energy of 122 MeV/u are compared to simulations of the axial beam dynamics. Ions confined in the bucket are addressed by the narrow-band force of a laser beam counter-propagating to the ion beam, while the laser frequency is detuned relatively to the cooling transition frequency in the rest frame of the bucket. At large detuning comparable to the momentum acceptance of the bucket, the axial dynamics can be well explained by the secular motion of individual non-interacting ions. At small detuning, corresponding to a small axial momentum spread Δpax…