47538620
VMM1 - An ASIC for micropattern detectors
We present VMM1, the first prototype of a family of front-end ASICs designed for the ATLAS muon upgrade. The ASIC will operate with MICRO MEG AS and TGC detectors providing charge and timing measurements along with a number of features including sub-hysteresis discrimination, address of the first event in real time, and digital output per channel for Time-over-Threshold measurements. The shaper, designed using the concept of Delayed Dissipative Feedback (DDF), allows analog dynamic ranges in excess of 10,000. With a capacitance of 200 pF and a nominal peaking time of 25 ns it can provide charge and timing resolution below 1 fC and Ins respectively, for input charges up to 2 pc. Designed in a commercial 130 nm technology it dissipates about 4.5 mW per channel.
109836098
Design and characterization of the VMM1 ASIC for micropattern gas detectors
Abstract Measurements of the first prototype VMM1 ASIC designed at Brookhaven National Laboratory in 130 nm CMOS and fabricated in spring 2012 are presented. The 64-channel ASIC features a novel design for use with several types of micropattern gas detectors. The data driven system measures peak amplitude and timing information in tracking mode including sub-threshold neighbors and first channel hit address in trigger mode. Several programmable gain and integration times allows the flexibility to work with Micromegas, Thin Gap Chambers (TGCs), and Gas Electron Multiplier (GEM) detectors. The IC design and features are presented along with measurements characterizing the performance of the VMM1 such as noise, linearity of the response, time walk, and calibration range.
37649879
LAr TPC Electronics CMOS Lifetime at 300 K and 77 K and Reliability Under Thermal Cycling
A study of hot-carrier effects (HCE) on the 180-nm CMOS device lifetime has been performed at 300 K and 77 K for Liquid Argon Time Projection Chamber (LAr TPC). Two different measurements were used: accelerated lifetime measurement under severe electric field stress by the drain-source voltage Vds, and a separate measurement of the substrate current as a function of 1/Vds. The former verifies the canonical very steep slope of the inverse relation between the lifetime and the substrate current, and the latter confirms that below a certain value of Vds a lifetime margin of several orders of magnitude can be achieved for the cold electronics TPC readout. The low power ASIC design for LAr TPC falls naturally into this domain, where hot-electron effects are negligible. Lifetime of digital circuits (ac operation) is extended by the inverse duty factor 1/(fclockteff) compared to dc operation. This factor is large (> 100) for deep submicron technology and clock frequency needed for TPC readout. As an additional margin, Vds may be reduced by ~ 10%. Extremely low failure rate (incidence) in previous large experiments demonstrates that surface mount circuit board technology withstands very well even multiple abrupt immersion in liquid nitrogen applied in board testing, and that the total failure incidence in continuous operation over time is very low.
16179887
First calculation of cosmic-ray muon spallation backgrounds for MeV astrophysical neutrino signals in Super-Kamiokande
signals is much larger than the signal rates for kinetic energies of about 6 { 18 MeV. Surprisingly, there is no published calculation of the production and properties of these backgrounds in water, though there are such studies for scintillator. Using the simulation code FLUKA and theoretical insights, we detail how muons lose energy in water, produce secondary particles, how and where these secondaries produce isotopes, and the properties of the backgrounds from their decays. We reproduce Super-Kamiokande measurements of the total background to within a factor of 2, which is good given that the isotope yields vary by orders of magnitude and that some details of the experiment are unknown to us at this level. Our results break aggregate data into component isotopes, reveal their separate production mechanisms, and preserve correlations between them. We outline how to implement more eective background rejection techniques using this information. Reducing backgrounds in solar and DSNB studies by even a factor of a few could help lead to important new discoveries.
204940116
power counting of various Dirac covariants in hadronic Bethe-Salpeter wave functions for decay constant calculations of pseudoscalar mesons
We have employed the framework of Bethe-Salpeter equation under covariant instantaneous ansatz to calculate leptonic decay constants of unequal mass pseudoscalar mesons like π, K, D, Ds and B and radiative decay constants of neutral pseudoscalar mesons like π0 and ηc in two photons. In the Dirac structure of hadronic Bethe-Salpeter wave function, the covariants are incorporated from their complete set in accordance with a recently proposed power counting rule. The decay constants are calculated with the incorporation of both Leading order and Next-to-leading order Dirac covariants. The results validate the power counting rule which provides a practical means of incorporating Dirac covariants in the Bethe-Salpeter wave function for a hadron.
118488945
Current leads for superconducting magnets of ADS injector I
In an ADS injector I, there are five superconducting magnets in each cryomodule. Each superconducting magnet contains a solenoid magnet, a horizontal dipole corrector (HDC), and a vertical dipole corrector (VDC). Six current leads will be required to power the electrical circuits, from room temperature to the 2.1 K liquid helium bath: two leads carry 100 A current for the solenoid magnet while the other four carry 12 A for the HDC and the VDC. This paper presents the principle of current lead optimization, which includes the cooling methods, the choice of material and structure, and the issues for current lead integration.
14118127
The Bifurcation of the Topological Structure in the Sunspot's Electric Topological Current with Locally Gauge-invariant Maxwell-Chern-Simons Term
The topological structure of the electric topological current of the locally gauge invariant Maxwell-Chern-Simons Model and its bifurcation is studied. The electric topological charge is quantized in term of winding number. The Hopf indices and Brouwer degree labeled the local topological structure of the electric topological current. Using Φ-mapping method and implicit function theory, the electric topological current is found generating or annihilating at the limit points and splitting or merging at the bifurcate points. The total electric charge holds invariant during the evolution.
13962394
Combination of Heavy Quark with Partons from Quark-Gluon Matter: a Scaling Probe
In relativistic heavy ion collisions, the cross section of heavy hadron production via the combination of a heavy quark with a light one from the quark-gluon matter can be factorized. It is the convolution of twist-4 combination matrix elements, the parameters corresponding to the parton distributions of the quark-gluon matter, as well as the hard partonic cross section of heavy quark production calculable in PQCD. These parton distributions and combination matrix elements are functions of a scaling variable which is the momentum fraction of the heavy quark w.r.t. the heavy hadron. In the same factorization framework, the combination matrix elements appear in other `simpler' processes and can be extracted. Taking them as inputs, comparing with data from RHIC and (future) LHC, we can get the parton distributions of the quark-gluon matter just as the similar way we get those of nucleon, pion, or photon, etc..