3,367 research outputs found
Measurement of XeI and XeII velocity in the near exit plane of a low-power Hall effect thruster by light induced fluorescence spectroscopy
Near exit plane non-resonant light induced fluorescence spectroscopy is
performed in a Hall effect low-power Xenon thruster at discharge voltage of
250V and anode flow rate of 0.7mg/sec. Measurement of the axial and radial
velocity components are performed, exciting the 6s[3/2]_2-->6p[3/2]_2
transition at 823.16nm in XeI and the 5d[4]_(7/2)-->6p[3]_(5/2) transition at
834.724nm in XeII. No significant deviation from the thermal velocity is
observed for XeI. Two most probable ion velocities are registered at a given
position with respect to the thruster axis, which are mainly attributed to
different areas of creation of ions inside the acceleration channel. The
spatial resolution of the set-up is limited by the laser beam size (radius of
the order of 0.5mm) and the fluorescence collection optics, which have a view
spot diameter of 8mm.Comment: 6 pages, 8 figure
Polarizations of J/\psi and \psi' in hadroproduction at Tevatron in the k_t factorization approach
We present a calculation for the polarizations of and
produced in the hadron collisions at the Fermilab Tevatron. Various color octet
channels including , , and as
well as contributions from decays are considered in the
factorization approach. We find that in a rather wide range of the transverse
momenta of and , the production rates could be dominated by the
channel, and the predicted polarizations from the
channel and feeddown contributions are roughly
compatible with the preliminary CDF data. This might provide a possible release
from the conflict between the NRQCD collinear parton model calculations and the
CDF data.Comment: 12 pages, 4 PS files, final version for publicatio
Laser cooling of a trapped two-component Fermi gas
The collective Raman cooling of a trapped two-component Fermi gas is
analyzed. We develop the quantum master equation that describes the collisions
and the laser cooling, in the festina lente regime, where the heating due to
photon reabsorption can be neglected. The numerical results based on Monte
Carlo simulations show, that three-dimensional temperatures of the order of
0.008 T_F can be achieved. We analyze the heating related to the background
losses, and conclude that our laser-cooling scheme can maintain the temperature
of the gas without significant additional losses. Finally we derive an analytic
expression for the temperature of a trapped Fermi gas heated by background
collisions, that agrees very well with the data obtained from the numerical
simulation.Comment: 5 pages, 3 figure
Density Waves in Layered Systems with Fermionic Polar Molecules
A layered system of two-dimensional planes containing fermionic polar
molecules can potentially realize a number of exotic quantum many-body states.
Among the predictions, are density-wave instabilities driven by the anisotropic
part of the dipole-dipole interaction in a single layer. However, in typical
multilayer setups it is reasonable to expect that the onset and properties of a
density-wave are modified by adjacent layers. Here we show that this is indeed
the case. For multiple layers the critical strength for the density-wave
instability decreases with the number of layers. The effect depends on density
and is more pronounced in the low density regime. The lowest solution of the
instability corresponds to the density waves in the different layers being
in-phase, whereas higher solutions have one or several adjancet layers that are
out of phase. The parameter regime needed to explore this instability is within
reach of current experiments.Comment: 7 pages, 4 figures. Final version in EPJD, EuroQUAM special issue
"Cold Quantum Matter - Achievements and Prospects
The Investigations Of Beam Extraction And Collimation At U-70 Proton Synchrotron Of IHEP By Using Short Silicon Crystals
The new results of using short (2-4mm) bent crystals for extraction and
collimation of proton beam at IHEP 70 Gev proton synchrotron are reported. A
broad range of energies from 6 to 65 GeV has been studied in the same crystal
collimation set-up. The efficiency of extraction more than 85% and intensity
more than 10E12 were obtained by using crystal with the length 2-mm and the
angle 1 mrad. The new regime of extraction is applied now at the accelerator to
deliver the beam for different experimental setups within the range of
intensity 10E7-10E12ppp.Comment: Presented at EPAC 2002 (Paris, June 3-7), 3p
Design, status and perspective of the Mu2e crystal calorimeter
The Mu2e experiment at Fermilab will search for the charged lepton flavor
violating process of neutrino-less coherent conversion in the field
of an aluminum nucleus. Mu2e will reach a single event sensitivity of about
that corresponds to four orders of magnitude improvements
with respect to the current best limit. The detector system consists of a straw
tube tracker and a crystal calorimeter made of undoped CsI coupled with Silicon
Photomultipliers. The calorimeter was designed to be operable in a harsh
environment where about 10 krad/year will be delivered in the hottest region
and work in presence of 1 T magnetic field. The calorimeter role is to perform
/e separation to suppress cosmic muons mimiking the signal, while
providing a high level trigger and a seeding the track search in the tracker.
In this paper we present the calorimeter design and the latest RD results.Comment: 4 pages, conference proceeding for a presentation held at TIPP'2017.
To be published on Springer Proceedings in Physic
The Mu2e undoped CsI crystal calorimeter
The Mu2e experiment at Fermilab will search for Charged Lepton Flavor
Violating conversion of a muon to an electron in an atomic field. The Mu2e
detector is composed of a tracker, an electromagnetic calorimeter and an
external system, surrounding the solenoid, to veto cosmic rays. The calorimeter
plays an important role to provide: a) excellent particle identification
capabilities; b) a fast trigger filter; c) an easier tracker track
reconstruction. Two disks, located downstream of the tracker, contain 674 pure
CsI crystals each. Each crystal is read out by two arrays of UV-extended SiPMs.
The choice of the crystals and SiPMs has been finalized after a thorough test
campaign. A first small scale prototype consisting of 51 crystals and 102 SiPM
arrays has been exposed to an electron beam at the BTF (Beam Test Facility) in
Frascati. Although the readout electronics were not the final, results show
that the current design is able to meet the timing and energy resolution
required by the Mu2e experiment.Comment: 6 pages, 8 figures, proceedings of the "Calorimetry for the high
energy frontier (CHEF17)" conference, 2-6 October 2017, Lyon, Franc
Quality Assurance on a custom SiPMs array for the Mu2e experiment
The Mu2e experiment at Fermilab will search for the coherent
conversion on aluminum atoms. The detector system consists of a straw tube
tracker and a crystal calorimeter. A pre-production of 150 Silicon
Photomultiplier arrays for the Mu2e calorimeter has been procured. A detailed
quality assur- ance has been carried out on each SiPM for the determination of
its own operation voltage, gain, dark current and PDE. The measurement of the
mean-time-to-failure for a small random sample of the pro-production group has
been also completed as well as the determination of the dark current increase
as a function of the ioninizing and non-ioninizing dose.Comment: 4 pages, 10 figures, conference proceeding for NSS-MIC 201
Energy and time resolution for a LYSO matrix prototype of the Mu2e experiment
We have measured the performances of a LYSO crystal matrix prototype tested
with electron and photon beams in the energy range 60450 MeV. This study has
been carried out to determine the achievable energy and time resolutions for
the calorimeter of the Mu2e experiment.Comment: 2 pages, 3 figures, 13th Pisa Meeting on Advanced Detector
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