The ALTO project at IPN Orsay

In order to probe neutron rich radioactive noble gases produced by photo-fission, a PARRNe1 experiment (Production d'Atomes Radioactifs Riches en Neutrons) has been carried out at CERN. The incident electron beam of 50 MeV was delivered by the LIL machine: LEP Injector Linac. The experiment allowed to compare under the same conditions two production methods of radioactive noble gases: fission induced by fast neutrons and photo-fission. The obtained results show that the use of the electrons is a promising mode to get intense neutron rich ion beams. Thereafter, the success of this photo-fission experiment, a conceptual design for the installation at IPN Orsay of a 50 MeV electron accelerator close to the PARRNe-2 device has been worked out: ALTO Project. This work has started within a collaboration between IPNO, LAL and CERN groups.Comment: 14 pages, pdf file, International School-Seminar on Heavy-Ion Physics 7 (2002

REXEBIS the Electron Beam Ion Source for the REX-ISOLDE project

The REXEBIS is an Electron Beam Ion Source (EBIS) developed especially to trap and further ionise the sometimes rare and short-lived isotopes that are produced in the ISOLDE separator for the Radioactive beam EXperiment at ISOLDE (REX-ISOLDE). By promoting the single-charged ions to a high charge-state the ions are more efficiently accelerated in the following linear accelerator. The EBIS uses an electron gun capable of producing a 0.5 A electron beam. The electron gun is immersed in a magnetic field of 0.2 T, and the electron beam is compressed to a current density of >200 A/cm2 inside a 2 T superconducting solenoid. The EBIS is situated on a high voltage (HV) platform with an initial electric potential of 60 kV allowing cooled and bunched 60 keV ions extracted from a Penning trap to be captured. After a period of confinement in the electron beam (<20 ms), the single-charged ions have been ionised to a charge-to-mass ratio of approximately ¼. During this confinement period, the platform potential is decreased to about 20 kV, and an axial potential barrier is lowered to allow the now highly charged ions to be extracted from the EBIS at an energy matching the requirement of the Radio Frequency Quadrupole (RFQ). Several different topics are presented in this report, all connected with the design and construction of an EBIS. Old 'truths' have also been scrutinised, for instance alignment tolerances. A large part is devoted to the description of a novel EBIS simulation implementation. A complete injection, breeding and extraction cycle has been simulated to certify high injection and extraction efficiencies. The entire EBIS was modelled in an ion-tracing program called SIMION, and the accepted and emitted phase spaces were determined. Beam optics parameters such as lens positions, voltages, accepted beam-tilt and displacement tolerances at the focal points were also settled using SIMION. An analytically derived acceptance formula was verified with simulations, and general conclusions on acceptance, emittance and energy spread of an EBIS are presented in this report. Any possible correlation between the two transverse phase spaces was shown to be insignificant. Furthermore, continuous injection, and maximal obtainable efficiency for such an injection mode were studied theoretically. The electron reflection and back-scattering in the collector was simulated using a combination of EGUN and SIMION. The result showed that a much lower degree of electron back-scattering may be obtained with this design as compared to previously published estimations. Furthermore, the Penning trapping of electrons at the trap barrier (or the post anode) was addressed, and techniques to avoid it were evaluated. Vacuum considerations for residual gas in the warm-bore magnet chamber, and the back-flow of Ar cooling gas from the Penning trap, have also been addressed since there is a risk of outnumbering the small number of radioactive ions. Simulated extraction spectra for different pressure scenarios are presented. All different REXEBIS elements (magnet, electron gun, inner structure, collector etc) are described from a design and performance perspective, and preliminary investigations of the platform high voltage switching and the beam diagnostics are included as well. A very elegant and simple method to align the solenoid within the iron yoke was developed and used. The high experimental emittance value obtained for electron beam ion source at MSL in Stockholm (4 times larger than the absolute upper theoretical value) was reproduced in simulations and could be justified by aberrations in the small einzel lens following the collector. The result of this simulation also verified the validity of the developed EBIS code

Waveform Identification of Altimetry Satellite Data of Shallow and Deep Waters in Southern Java Waters

Waveform patterns of satellite altimetry affect the accuracy of sea surface height estimation from the satellite. The waveform patterns found in the coastal waters are generally not in the ideal form (Brown-waveform), resulting inaccurate in sea surface height estimation. The objec-tives of this research were to identify patterns of the waveform and determine their variability. Satellite altimetry Jason-2 SGDR (Sensor Geophysical Data Record) type D data located in the southern Java island waters of the year of 2013 were used and downloaded from “NOAA's Comprehensive Large Array-data Stewardship System” (www.class.ncdc.noaa.gov) . Waveform identification and analyses were conducted along the satellite pass within the distance of 0-10 km, 10-50 km, and 50-100 km form the coastline. Results showed that the highest number of non-Brown-waveform was found within 0-10 km of the coastline (69%). Meanwhile, within the distance of 10-50 km and 50-100 km from the coastline, the number of non-Brown waveform was 5% and 3%, respectively. Brown waveform patterns could be found generally starting at 7.58 km from the coastline. Factors such as land near coastal waters, the depth and shape of the surface waters, aerosols in the atmosphere, building (example: lighthouse or ship) found in coastal areas suspected to be the cause of the noise in waveforms

Spin polarization in a two-dimensional electron gas

We evaluate the charge and longitudinal spin response functions of a two-dimensional electron gas with $e^2/r$ interactions in an arbitrary state of spin polarization, using a structurally self-consistent approach to treat exchange and correlations. From the results we assess the nature of the magnetic order in the electronic ground state in zero magnetic field as a function of electron density. We find that states of partial spin polarization are thermodynamically unstable at all values of the coupling strength and that a first-order phase transition occurs with increasing coupling strength from the magnetically disorderd (paramagnetic) phase to the fully spin-polarized (ferromagnetic) phase. This behavior is in qualitative agreement with diffusion Monte Carlo data, although the location of the phase transition is underestimated in our calculations.Comment: 12 pages, 10 figuer

Studi Kerapatan dan Perubahan Tutupan Mangrove Menggunakan Citra Satelit di Pulau Sebatik Kalimantan Utara

Hutan mangrove merupakan ekosistem yang rentan sehingga membutuhkan pemantauan terus menerus untuk mendeteksi berbagai ancaman seperti aktivitas manusia dan bencana alam. Penginderaan jarak jauh dan sistem informasi geografis (SIG) sangat efektif untuk digunakan dalam pemantauan ekosistem mangrove karena dapat menjangkau daerah yang luas dan dapat dilakukan sekala berkala. Penerapan teknologi penginderaan jarak jauh untuk memantau ekosistem mangrove di Pulau Sebatik belum pernah dilakukan sebelumnya. Penelitian ini penting untuk mengetahui Perubahan kondisi hutan mangrove di Pulau Sebatik. Tujuan dari penelitian ini adalah untuk menghitung akurasi klasifikasi tutupan lahan dengan resolusi spasial yang berbeda, mengukur Perubahan mangrove dari tahun 2005 sampai 2016, dan menganalisis korelasi antara nilai Normalized Different Vegetation Index (NDVI) dan persentase tutupannya. Klasifikasi tutupan lahan dalam penelitian ini menggunakan klasifikasi terbimbing dengan algoritma Maximum Likelihood. NDVI digunakan sebagai indikator kerapatan mangrove. Pengukuran data lapangan diambil untuk menghitung tutupan kanopi. Penilaian akurasi klasifikasi citra Landsat sekitar 83% dan citra SPOT 6 sekitar 90%. Mangrove di Pulau Sebatik mengalami peningkatan dari tahun 2005 sampai 2016 sebesar 31,27%. Korelasi antara tutupan NDVI dan kanopi dikategorikan tinggi dengan koefisien korelasi r = 0,82 (Landsat 8) dan 0,85 (SPOT 6)

Observation of Unbound States in 16Ne/15Ne^{16}Ne / ^{15}Ne via 1n- / 2n-Knockout on 17Ne^{17}Ne

ISSN:0022-2461ISSN:1573-480