40,062 research outputs found
Irradiation Tests and Expected Performance of Readout Electronics of the ATLAS Hadronic Endcap Calorimeter for the HL-LHC
The readout electronics of the ATLAS Hadronic Endcap Calorimeter (HEC) will
have to withstand an about 3-5 times larger radiation environment at the future
high-luminosity LHC (HLLHC) compared to their design values. The preamplifier
and summing boards (PSBs), which are equipped with GaAs ASICs and comprise the
heart of the readout electronics, were irradiated with neutrons and protons
with fluences surpassing several times ten years of operation of the HL-LHC.
Neutron tests were performed at the NPI in Rez, Czech Republic, where a 36 MeV
proton beam was directed on a thick heavy water target to produce neutrons. The
proton irradiation was done with 200 MeV protons at the PROSCAN area of the
Proton Irradiation Facility at the PSI in Villigen, Switzerland. In-situ
measurements of S-parameters in both tests allow the evaluation of frequency
dependent performance parameters, like gain and input impedance, as a function
of fluence. The linearity of the ASIC response was measured directly in the
neutron tests with a triangular input pulse of varying amplitude. The results
obtained allow an estimation of the expected performance degradation of the
HEC. For a possible replacement of the PSB chips, alternative technologies were
investigated and exposed to similar neutron radiation levels. In particular,
IHP 250 nm Si CMOS technology has turned out to show good performance and match
the specifications required. The performance measurements of the current PSB
devices, the expected performance degradations under HL-LHC conditions, and
results from alternative technologies will be presented.Comment: 5 pages, 4 figures, CHEF2013 Conference Proceedings. arXiv admin
note: text overlap with arXiv:1301.375
Liaison classes of modules
We propose a concept of module liaison that extends Gorenstein liaison of
ideals and provides an equivalence relation among unmixed modules over a
commutative Gorenstein ring. Analyzing the resulting equivalence classes we
show that several results known for Gorenstein liaison are still true in the
more general case of module liaison. In particular, we construct two maps from
the set of even liaison classes of modules of fixed codimension into stable
equivalence classes of certain reflexive modules. As a consequence, we show
that the intermediate cohomology modules and properties like being perfect,
Cohen-Macaulay, Buchsbaum, or surjective-Buchsbaum are preserved in even module
liaison classes. Furthermore, we prove that the module liaison class of a
complete intersection of codimension one consists of precisely all perfect
modules of codimension one
Swap-invariant and exchangeable random measures
In this work we analyze the concept of swap-invariance, which is a weaker
variant of exchangeability. A random vector in is called
swap-invariant if is
invariant under all permutations of for each . We extend this notion to random measures. For a swap-invariant
random measure on a measure space the vector
is swap-invariant for all disjoint with equal -measure. Various characterizations of
swap-invariant random measures and connections to exchangeable ones are
established. We prove the ergodic theorem for swap-invariant random measures
and derive a representation in terms of the ergodic limit and an exchangeable
random measure. Moreover we show that diffuse swap-invariant random measures on
a Borel space are trivial. As for random sequences two new representations are
obtained using different ergodic limits.Comment: 30 pages; v2: variant of ergodic theorem and example added, minor
changes in text; v3: structure changed, theorems slightly improve
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