arXiv subjects

R. Stanek

Publications and source records attributed to R. Stanek.

11 recordsLinked to original sources

arXiv2023

PIII Project Overview and Status

The Proton Improvement Plan II (PIP-II) project is an essential upgrade to Fermilab's particle accelerator complex to enable the world's most intense neutrino beam for LBNF/DUNE and a broad particle physics program for many decades to come. PIP-II will deliver 1.2 MW of proton beam power from the Main Injector, upgradeable to multi-MW capability. The central element of PIP-II is an 800 MeV superconducting radio frequency (SRF) linac, which comprises a room temperature front end followed by an SRF section. The SRF section consists of five different flavors of cavities/cryomodules, including Half Wave Resonators (HWR), Single Spoke and elliptical resonators operating at, or above, state-of-the-art parameters. The first two PIP-II cryomodules, Half Wave Resonator (HWR) and Single Spoke Resonator 1 (SSR1) were installed in the PIP-II Injector Test facility (PIP2IT) and have accelerated beam to above 17 MeV. PIP-II is the first U.S. accelerator project that will be constructed with significant contributions from international partners, including India, Italy, France, United Kingdom and Poland. The project was baselined in April 2022, and the construction phase is underway.

physics.acc-ph↗

arXiv2019

Achievement of Ultra-High Quality Factor in Prototype Cryomodule for LCLS-II

Quality factor is a primary cost driver for high energy, continuous wave (CW) SRF linacs like the LCLS-II X-ray free electron laser currently under construction. Taking this into account, several innovations were introduced in the LCLS-II cryomodule design to push substantially beyond the previous state-of-the-art quality factor achieved in operation. This includes the first ever implementation of the nitrogen doping cavity treatment, the capability to provide high mass flow cooldown to improve expulsion of magnetic flux based on recent R&D, high performance magnetic shielding, and other critical subcomponents. To evaluate the implementation of these new cryomodule features, two prototype cryomodules were produced. In this paper, we present results from the prototype cryomodule assembled at Fermilab, which achieved unprecedented cavity quality factors of 3.0e10 at a nominal cryomodule voltage. We overview cavity performance, procedures to achieve ambient magnetic field < 5 mG at the cavity wall, and the successful demonstration of high mass flow cooldown in a cryomodule. The cavity performance under various cool down conditions are presented as well to show the impact of flux expulsion on Q0.

physics.acc-ph↗

arXiv2018

Commissioning And First Results From The Fermilab Cryomodule Test Stand

A new test stand dedicated to Superconducting Radiofrequency (SRF) cryomodule testing, CMTS1, has been commissioned and is now in operation at Fermilab. The first device to be cooled down and powered in this facility is the prototype 1.3 GHz cryomodule assembled at Fermilab for LCLS-II. We describe the demonstrated capabilities of CMTS1, report on steps taken during commissioning, provide an overview of first test results, and survey future plans.

physics.acc-ph↗

arXiv2014

The Project-x Injector Experiment: A Novel High Performance Front-end For A Future High Power Proton Facility At Fermilab

A multi-MW proton facility, Project X, has been proposed and is currently under development at Fermilab. We are carrying out a program of research and development aimed at integrated systems testing of critical components comprising the front end of Project X. This program, known as the Project X Injector Experiment (PXIE), is being undertaken as a key component of the larger Project X R&D program. The successful completion of this program will validate the concept for the Project X front end, thereby minimizing a primary technical risk element within Project X. PXIE is currently under construction at Fermilab and will be completed over the period FY12-17. PXIE will include an H- ion source, a CW 2.1-MeV RFQ and two superconductive RF (SRF) cryomodules providing up to 25 MeV energy gain at an average beam current of 1 mA (upgradable to 2 mA). Successful systems testing will also demonstrate the viability of novel front end technologies that are expected find applications beyond Project X.

physics.acc-ph↗

arXiv2011

New Optical Link Technologies for HEP Experiments

As a concern with the reliability and mass of current optical links in LHC experiments, we are investigating CW lasers and light modulators as an alternative to VCSELs. In addition we are developing data links in air, utilizing steering by MEMS mirrors and optical feedback paths for the control loop. Laser, modulator, and lens systems used are described, as well as two different electronic systems for a free space steering feedback loop. Our prototype system currently operates at 1.25 Gb/s, but could be upgraded. This link works over distances of order meters. Such links might enable one to move communication lasers (e.g. VCSELs) and optical fibers out of tracking detectors, for reasons such as reliability and power consumption. Some applications for free space data links, such as local triggering and data readout and trigger-clock distribution and links for much longer distances are also discussed.

physics.ins-det↗

arXiv2009

Massive Halos in Millennium Gas Simulations: Multivariate Scaling Relations

The joint likelihood of observable cluster signals reflects the astrophysical evolution of the coupled baryonic and dark matter components in massive halos, and its knowledge will enhance cosmological parameter constraints in the coming era of large, multi-wavelength cluster surveys. We present a computational study of intrinsic covariance in cluster properties using halo populations derived from Millennium Gas Simulations (MGS). The MGS are re-simulations of the original 500 Mpc/h Millennium Simulation performed with gas dynamics under two different physical treatments: shock heating driven by gravity only (GO) and a second treatment with cooling and preheating (PH). We examine relationships among structural properties and observable X-ray and Sunyaev-Zel'dovich (SZ) signals for samples of thousands of halos with M_200 > 5 \times 10^{13} Msun/h and z < 2. While the X-ray scaling behavior of PH model halos at low-redshift offers a good match to local clusters, the model exhibits non-standard features testable with larger surveys, including weakly running slopes in hot gas observable--mass relations and ~10% departures from self-similar redshift evolution for 10^14 Msun/h halos at redshift z ~ 1. We find that the form of the joint likelihood of signal pairs is generally well-described by a multivariate, log-normal distribution, especially in the PH case which exhibits less halo substructure than the GO model. At fixed mass and epoch, joint deviations of signal pairs display mainly positive correlations, especially the thermal SZ effect paired with either hot gas fraction (r=0.88/0.69 for PH/GO at z=0) or X-ray temperature (r=0.62/0.83). We discuss halo mass selection by signal pairs, and find a minimum mass scatter of 4% in the \PH model by combining thermal SZ and gas fraction measurements.

astro-ph.CO↗

arXiv2008

The Effect of Gas Physics on the Halo Mass Function

Cosmological tests based on cluster counts require accurate calibration of the space density of massive halos, but most calibrations to date have ignored complex gas physics associated with halo baryons. We explore the sensitivity of the halo mass function to baryon physics using two pairs of gas-dynamic simulations that are likely to bracket the true behavior. Each pair consists of a baseline model involving only gravity and shock heating, and a refined physics model aimed at reproducing the observed scaling of the hot, intracluster gas phase. One pair consists of billion-particle re-simulations of the original 500 Mpc/h Millennium Simulation of Springel et al. (2005), run with the SPH code Gadget-2 and using a refined physics treatment approximated by preheating (PH) at high redshift. The other pair are high-resolution simulations from the adaptive-mesh refinement code ART, for which the refined treatment includes cooling, star formation, and supernova feedback (CSF). We find that, although the mass functions of the gravity-only (GO) treatments are consistent with the recent calibration of Tinker et al. (2008), both pairs of simulations with refined baryon physics show significant deviations. Relative to the GO case, the masses of ~10^{14} Msun/h halos in the PH and CSF treatments are shifted by averages of -15 \pm 1 percent and +12 \pm 5 percent, respectively. These mass shifts cause ~ 30% deviations in number density relative to the Tinker function, significantly larger than the 5% statistical uncertainty of that calibration.

astro-ph↗

arXiv2008

The L_X--M relation of Clusters of Galaxies

We present a new measurement of the scaling relation between X-ray luminosity and total mass for 17,000 galaxy clusters in the maxBCG cluster sample. Stacking sub-samples within fixed ranges of optical richness, N_200, we measure the mean 0.1-2.4 keV X-ray luminosity, , from the ROSAT All-Sky Survey. The mean mass, , is measured from weak gravitational lensing of SDSS background galaxies (Johnston et al. 2007). For 9 <= N_200 < 200, the data are well fit by a power-law, /10^42 h^-2 erg/s = (12.6+1.4-1.3 (stat) +/- 1.6 (sys)) ( /10^14 h^-1 M_sun)^1.65+/-0.13. The slope agrees to within 10% with previous estimates based on X-ray selected catalogs, implying that the covariance in L_X and N_200 at fixed halo mass is not large. The luminosity intercent is 30%, or 2σ, lower than determined from the X-ray flux-limited sample of Reiprich & Bohringer (2002), assuming hydrostatic equilibrium. This difference could arise from a combination of Malmquist bias and/or systematic error in hydrostatic mass estimates, both of which are expected. The intercept agrees with that derived by Stanek et al. (2006) using a model for the statistical correspondence between clusters and halos in a WMAP3 cosmology with power spectrum normalization sigma_8 = 0.85. Similar exercises applied to future data sets will allow constraints on the covariance among optical and hot gas properties of clusters at fixed mass.

astro-ph↗

arXiv2007

Effects of Selection and Covariance on X-ray Scaling Relations of Galaxy Clusters

We explore how the behavior of galaxy cluster scaling relations are affected by flux-limited selection biases and intrinsic covariance among observable properties. Our models presume log-normal covariance between luminosity (L) and temperature (T) at fixed mass (M), centered on evolving, power-law mean relations as a function of host halo mass. Selection can mimic evolution; the \lm and \lt relations from shallow X-ray flux-limited samples will deviate from mass-limited expectations at nearly all scales while the relations from deep surveys ($10^{-14} \cgsflux$) become complete, and therefore unbiased, at masses above $\sims 2 \times 10^{14} \hinv \msol$. We derive expressions for low-order moments of the luminosity distribution at fixed temperature, and show that the slope and scatter of the \lt relation observed in flux-limited samples is sensitive to the assumed \lt correlation coefficient. In addition, \lt covariance affects the redshift behavior of halo counts and mean luminosity in a manner that is nearly degenerate with intrinsic population evolution.

astro-ph↗

arXiv2006

The X-Ray Luminosity--Mass Relation for Local Clusters of Galaxies

We investigate the relationship between soft \xray luminosity and mass for low redshift clusters of galaxies by comparing observed number counts to expectations of $Λ$CDM cosmologies. We use a three-parameter model for the conditional probability of luminosity given mass and epoch, described as a log-normal distribution of fixed width centered on a power-law scaling relation, $L \spropto M^p\rhoc^s(z)$. We use an ensemble of simulated clusters to argue that the observed, intrinsic variance in the temperature--luminosity relation is directly indicative of mass--luminosity variance, and derive $\sigm \se 0.43 \pm 0.06$ from HIFLUGCS data. Adding this to the likelihood analysis results in best-fit estimates $p \se 1.59 \pm 0.05$, $\lnlf \se 1.34 \pm 0.09$, and $\sigm \se 0.37 \pm 0.05$ for self-similar redshift evolution in a concordance ($Ω_m \se 0.3$, $Ω_Λ\se 0.7$, $σ_8 \se0.9$) universe. We show that the present-epoch intercept is very sensitive to power spectrum normalization, $\lnlf \spropto \sigate^{-4}$, and the slope is weakly sensitive to the matter density, $p \spropto Ω_m^{1/2}$. The intercept derived here is dimmer by a factor 2, and slope slightly steeper, than the L-M relation published using hydrostatic mass estimates of the HIFLUGCS sample. We show that this discrepancy is largely due to Malmquist bias of the \xray\ flux-limited sample. In light of new WMAP constraints, we discuss the interplay between parameters and sources of systematic error, and offer a compromise model with $Ω_m \se 0.24$, $σ_8 \se 0.85$, and somewhat lower scatter $\sigm \se 0.25$, in which hydrostatic mass estimates remain accurate to $\ssim 15%$. We stress the need for independent calibration of the L-M relation via weak gravitational lensing.

astro-ph↗

arXiv2003

The CDFII Time-Of-Flight Detector and Impact on Beauty Flavor Tagging

The new CDFII detector incorporates a Time-of-Flight detector (TOF), employing plastic scintillator bars and fine-mesh photomultipliers. Since August 2001 the TOF system has been fully instrumented and integrated into the CDFII data acquisition system. With a design goal of $100 ps$ resolution the TOF system will provide at least two standard deviations separation between $K^{\pm}$ and $π^{\pm}$ for momenta $p<1.6 GeV/c$, complementing low momentum particle identification by means of the specific ionization energy loss measured in the drift chamber. We describe the design of the TOF detector and discuss the current status of its calibration and initial performances. Finally we review the expected impact of the TOF detector in the flavor tagging of neutral $B_S$ meson.

hep-ex↗