arXiv subjects

M. Xiao

Publications and source records attributed to M. Xiao.

43 records · Page 3Linked to original sources

arXiv2013

Development of the Liquid Level Meters for the PandaX Dark Matter Detector

The two-phase xenon detector is at the frontier of dark matter direct search. This kind of detector uses liquid xenon as the sensitive target and is operated in two-phase (liquid/gas) mode, where the liquid level needs to be monitored and controlled in sub-millimeter precision. In this paper, we present a detailed design and study of two kinds of level meters for the PandaX dark matter detector. The long level meter is used to monitor the overall liquid level while short level meters are used to monitor the inclination of the detector. These level meters are cylindrical capacitors custom-made from two concentric metal tubes. Their capacitance values are read out by a universal transducer interface chip and recorded by the PandaX slow control system. We present the developments that lead to level meters with long-term stability and sub-millimeter precision. Fluctuations (standard deviations) of less than 0.02 mm for the short level meters and less than 0.2 mm for the long level meter were achieved during a few days of test operation.

physics.ins-det↗

arXiv2013

Recycler Chromaticities and End Shims for NOvA at Fermilab

In era of NOvA operation, it is planned to slip-stack six on six Booster proton batches in the Recycler ring for a total intensity of 5 1013 protons/cycle. During the slip-stacking, the chromaticities are required to be jumped from (-2,-2) to (-20,-20). However, they can only be adjusted to (-12,-12) from (-2,-2) using existing 2 families of powered sextupoles. On the other hand, the presently designed Recycler lattice for Nova replaces the 30 straight section with 8 D-D half FODO cells . We use 3 quads in a half-cell to obtain the working point under the limit of the feasible quad strength, and the maximum beta-function in this section cannot be less than 80 m. In this paper, we re-designed the end shims of the permanent magnets in the ring lattice with appropriate quadrupole and sextupole components to meet both chromaticity and tune requirements. We are able to use 2 quads in a half cell in RR30 straight section within feasible quad strength. The maximum beta-functions are also lowered to around 55 m. The dynamic aperture tracking has been done using MAD to simulate the scenario of beam injection into the Recycler ring for Nova.

physics.acc-ph↗

arXiv2013

Transport from the Recycler Ring to the Antiproton Source Beamlines

In the post-Nova era, the protons are directly transported from the Booster ring to the Recycler ring rather than the Main Injector. For Mu2e and g-2 project, the Debuncher ring will be modified into a Delivery ring to deliver the protons to both Mu2e and g-2 experiemnts. Therefore, It requires the transport of protons from the Recycler Ring to the Delivery ring. A new transfer line from the Recycler ring to the P1 beamline will be constructed to transport proton beam from the Recycler Ring to existing Antiproton Source beamlines. This new beamline provides a way to deliver 8 GeV kinetic energy protons from the Booster to the Delivery ring, via the Recycler, using existing beam transport lines, and without the need for new civil construction. This paper presents the Conceptual Design of this new beamline.

physics.acc-ph↗

arXiv2012

Dynamic aperture and space charge effect studies for the Recycler ring for Project-X

A simplified Recycler lattice was created to fine tune injection straight, ring tune, and phase trombone. In this paper, we will present detailed modifications for further optimization of Recycler lattice which requires the investigation of tune footprint and dynamic aperture based on higher order momentum components of the magnetic fields, together with the space charge effects.

physics.acc-ph↗

arXiv2012

The electronic properties of graphene on metal modified SiO2 substrate

Based on first principles calculation, the electronic properties of graphene on metal (Ti, Ca, Ni, Mn, Co, Fe, Cr, K) modified SiO2 substrate have been studied. The results of binding energies supported graphene indicate that the metal atoms are adsorbed more stably on O surface than on Si surface of SiO2 substrate, and graphene is adsorbed very stably on metal modified substrate. The band structures of supported graphene are similar with that of suspending graphene when deposited on Co modified SiO2 surface, but change obviously with the effect of decorated Fe atoms. Interesting, a semi-metal band structure with a 1-2 eV gap in spin-up state will occur on the magnetic atoms decorated surface.

cond-mat.mes-hall↗

arXiv2009

Measurement of the Spin Relaxation Time of Single Electrons in a Silicon MOS-Based Quantum Dot

We report on measurements of the spin relaxation time T1 of individual electron spins in the few electron regime of a Si/SiO2-based quantum dot (QD). Energy-spectroscopy of the QD has been performed using a charge sensing technique. The spin relaxation times are subsequently measured in the time-domain by a pump-and-probe method. For the QD that contains an unpaired spin, likely only a single electron, we find that T1 depends strongly on the applied magnetic field. Possible mechanisms leading to the observed spin relaxation are discussed.

cond-mat.mes-hall↗

arXiv2006

Sputtered Gold as an Effective Schottky Gate for Strained Si/SiGe Nanostructures

Metallization of Schottky surface gates by sputtering Au on strained Si/SiGe heterojunctions enables the depletion of the two dimensional electron gas (2DEG) at a relatively small voltage while maintaining an extremely low level of leakage current. A fabrication process has been developed to enable the formation of sub-micron Au electrodes sputtered onto Si/SiGe without the need of a wetting layer.

cond-mat.mes-hall↗