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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

A SEARCH FOR ENHANCED VERY HIGH ENERGY GAMMA-RAY EMISSION FROM THE 2013 MARCH CRAB NEBULA FLARE

In 2013 March, a flaring episode from the Crab Nebula lasting ∼2 weeks was detected by Fermi-LAT (Large Area Telescope on board the Fermi Gamma-ray Space Telescope). The Very Energetic Radiation Imaging Telescope Array System (VERITAS) provides simultaneous observations throughout this period. During the flare, Fermi-LAT detected a 20 fold increase in flux above the average synchrotron flux >100 MeV seen from the Crab Nebula. Simultaneous measurements with VERITAS are consistent with the non-variable long-term average Crab Nebula flux at TeV energies. Assuming a linear correlation between the very high energy flux change >1 TeV and the flux change seen in the Fermi-LAT band >100 MeV during the period of simultaneous observations, the linear correlation factor can be constrained to be at most 8.6 × 10{sup –3} with 95% confidence.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

An equivalent circuit model and power calculations for the APS SPX crab cavities

An equivalent parallel resistor-inductor-capacitor (RLC) circuit with beam loading for a polarized TM110 dipole-mode cavity is developed and minimum radio-frequency (rf) generator requirements are calculated for the Advanced Photon Source (APS) short-pulse x-ray (SPX) superconducting rf (SRF) crab cavities. A beam-loaded circuit model for polarized TM110 mode crab cavities was derived. The single-cavity minimum steady-state required generator power has been determined for the APS SPX crab cavities for a storage ring current of 200mA DC current as a function of external Q for various vertical offsets including beam tilt and uncontrollable detuning. Calculations to aid machine protection considerations were given.

43 PARTICLE ACCELERATORS↗
DOE OSTI2017

Measurement of the Absolute Crab Flux with NuSTAR

We present results from a Nuclear Spectroscopic Telescope Array (NuSTAR) observation of the Crab made at a large off-axis angle of 1.°5. At these angles, X-rays do not pass through the optics and instead illuminate the detectors directly, due to incomplete baffling. Due to the simplicity of the instrument response in this configuration and the good absolute calibration of the detectors, we are able to measure the absolute intrinsic flux of the Crab to better than 4%. We find the spectral parameters of the power law to be Γ=2.106±0.006, N=9.71±0.16, in agreement with the values measured 42 years ago by Toor and Seward. This suggests that the observed variability of the Crab is not part of a long-term trend, but instead results from fluctuations around a steady mean. The NuSTAR observation also enabled improved measurement of the detector absorption parameters without the added complications of the mirror response.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

RADIO-TO-TeV PHASE-RESOLVED EMISSION FROM THE CRAB PULSAR: THE ANNULAR GAP MODEL

The Crab pulsar is a quite young, famous pulsar that radiates multi-wavelength pulsed photons. The latest detection of GeV and TeV pulsed emission with an unprecedented signal-to-noise ratio, supplied by the powerful telescopes Fermi, MAGIC, and VERITAS, challenges the current popular pulsar models, and can be a valuable discriminator to justify the pulsar high-energy-emission models. Our work is divided into two steps. First, taking reasonable parameters (the magnetic inclination angle {alpha} = 45 Degree-Sign and the view angle {zeta} = 63 Degree-Sign ), we use the latest high-energy data to calculate radio, X-ray, {gamma}-ray, and TeV light curves from a geometric view to obtain crucial information on emission locations. Second, we calculate the phase-averaged spectrum and phase-resolved spectra for the Crab pulsar and take a theoretical justification from a physical view for the emission properties as found in the first step. It is found that a Gaussian emissivity distribution with the peak emission near the null charge surface in the so-called annular gap (AG) region gives the best modeled light curves. The pulsed radio, X-ray, {gamma}-ray, and TeV emission are mainly generated from the emission of primary particles or secondary particles with different emission mechanisms in the nearly similar region of the AG located in the only magnetic pole, which leads to the nearly 'phase-aligned' multi-wavelength light curves. The emission of peak 1 and peak 2 originates from the AG region near the null charge surface, while the emission of the bridge primarily originates from the core gap (CG) region. The charged particles cannot co-rotate with the pulsar and escape from the magnetosphere, which determines the original flowing primary particles. The acceleration electric field and potential in the AG and CG are huge enough and are in the several tens of neutron star radii. Thus, the primary particles are accelerated to ultra-relativistic energies and produce numerous secondary particles (pairs) in the inner regions of the AG and CG. We emphasize that there are mainly two types of pairs: one is curvature-radiation induced (CR-induced) and the other is inverse-Compton-scattering induced (ICS-induced). The phase-averaged spectrum and phase-resolved spectra from soft X-ray to TeV bands are produced by four components: synchrotron radiation from CR- and ICS-induced pairs dominates the X-ray band to soft {gamma}-ray band (100 eV to 10 MeV); curvature radiation and synchrotron radiation from the primary particles mainly contribute to the {gamma}-ray band (10 MeV to {approx}20 GeV); ICS from the pairs significantly contributes to the TeV {gamma}-ray band ({approx}20-400 GeV). The multi-wavelength pulsed emission from the Crab pulsar can be well modeled with the AG and CG model. To distinguish our single magnetic pole model from two-pole models, the convincing values of the magnetic inclination angle and the viewing angle will play a key role.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

SEARCH FOR A CORRELATION BETWEEN VERY-HIGH-ENERGY GAMMA RAYS AND GIANT RADIO PULSES IN THE CRAB PULSAR

We present the results of a joint observational campaign between the Green Bank radio telescope and the VERITAS gamma-ray telescope, which searched for a correlation between the emission of very-high-energy (VHE) gamma rays (E {sub {gamma}} > 150 GeV) and giant radio pulses (GRPs) from the Crab pulsar at 8.9 GHz. A total of 15,366 GRPs were recorded during 11.6 hr of simultaneous observations, which were made across four nights in 2008 December and in 2009 November and December. We searched for an enhancement of the pulsed gamma-ray emission within time windows placed around the arrival time of the GRP events. In total, eight different time windows with durations ranging from 0.033 ms to 72 s were positioned at three different locations relative to the GRP to search for enhanced gamma-ray emission which lagged, led, or was concurrent with, the GRP event. Furthermore, we performed separate searches on main pulse GRPs and interpulse GRPs and on the most energetic GRPs in our data sample. No significant enhancement of pulsed VHE emission was found in any of the preformed searches. We set upper limits of 5-10 times the average VHE flux of the Crab pulsar on the flux simultaneous with interpulse GRPs on single-rotation-period timescales. On {approx}8 s timescales around interpulse GRPs, we set an upper limit of 2-3 times the average VHE flux. Within the framework of recent models for pulsed VHE emission from the Crab pulsar, the expected VHE-GRP emission correlations are below the derived limits.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Efficient monitoring of CRAB jobs at CMS

CRAB is a tool used for distributed analysis of CMS data. Users can submit sets of jobs with similar requirements (tasks) with a single request. CRAB uses a client-server architecture, where a lightweight client, a server, and ancillary services work together and are maintained by CMS operators at CERN. As with most complex software, good monitoring tools are crucial for efficient use and longterm maintainability. This work gives an overview of the monitoring tools developed to ensure the CRAB server and infrastructure are functional, help operators debug user problems, and minimize overhead and operating cost. This work also illustrates the design choices and gives a report on our experience with the tools we developed and the external ones we used.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Search for thermal X-ray features from the Crab nebula with the Hitomi soft X-ray spectrometer*

The Crab nebula originated from a core-collapse supernova (SN) explosion observed in 1054 A.D. When viewed as a supernova remnant (SNR), it has an anomalously low observed ejecta mass and kinetic energy for an Fe-core collapse SN. Intensive searches were made for a massive shell that solves this discrepancy, but none has been detected. An alternative idea is that the SN1054 is an electron-capture (EC) explosion with a lower explosion energy by an order of magnitude than Fe-core collapse SNe. In the X-rays, imaging searches were performed for the plasma emission from the shell in the Crab outskirts to set a stringent upper limit to the X-ray emitting mass. However, the extreme brightness of the source hampers access to its vicinity. We thus employed spectroscopic technique using the X-ray micro-calorimeter onboard the Hitomi satellite. By exploiting its superb energy resolution, we set an upper limit for emission or absorption features from yet undetected thermal plasma in the 2–12 keV range. We also re-evaluated the existing Chandra and XMM-Newton data. By assembling these results, a new upper limit was obtained for the X-ray plasma mass of ≲1 M⊙ for a wide range of assumed shell radius, size, and plasma temperature both in and out of the collisional equilibrium. To compare with the observation, we further performed hydrodynamic simulations of the Crab SNR for two SN models (Fe-core versus EC) under two SN environments (uniform ISM versus progenitor wind). We found that the observed mass limit can be compatible with both SN models if the SN environment has a low density of ≲ 0.03 cm -3 (Fe core) or ≲ 0.1 cm -3 (EC) for the uniform density, or a progenitor wind density somewhat less than that provided by a mass loss rate of 10 -5 M⊙ yr -1 at 20 km s -1 for the wind environment.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2024

Transverse emittance growth due to rf noise in crab cavities: Theory, measurements, cure, and high luminosity LHC estimates

The High-Luminosity LHC (HL-LHC) upgrade with planned operation from 2029 onward has a goal of achieving a tenfold increase in the integrated number of recorded collisions thanks to a doubling of the intensity per bunch ( 2.2 × 10 11 protons) and a reduction of β * (the β value in the two high luminosity detectors, namely ATLAS and CMS) to 15 cm. Such an increase in recorded collisions would significantly expedite new discoveries and exploration. Crab cavities are an important component of the HL-LHC upgrade and will contribute strongly to achieving an increase in the number of recorded collisions. However, noise injected through the crab cavity radio frequency (rf) system could cause significant transverse emittance growth and limit luminosity lifetime. We presented a theoretical formalism relating transverse emittance growth to rf noise in an earlier work. In this follow-up paper, we summarize measurements in the super-proton synchrotron (SPS) at CERN that validate the theory, we present estimates of the emittance growth rates using state-of-the-art rf and low-level rf (LLRF) technologies, and we set the rf noise specifications to achieve acceptable performance. A novel dedicated feedback system acting through the crab cavities to mitigate emittance growth will be required. In this work, we develop a theoretical formalism to evaluate the performance of such a feedback system in any collider, identify limiting components, present simulation results to validate these studies, and derive key design parameters for an HL-LHC implementation of such a feedback system. Published by the American Physical Society 2024

43 PARTICLE ACCELERATORS↗
DOE OSTI2013

Cryogenic test of a proof-of-principle superconducting rf-dipole deflecting and crabbing cavity

Recent applications in need of compact low-frequency deflecting and crabbing cavities have initiated the design and development of new superconducting structures operating at high gradients with low losses. Previously, TM{sub 110}-type deflecting and crabbing cavities had been developed and have also been in operation successfully. However these geometries are not favorable designs for low operating frequencies. The superconducting rf-dipole cavity is the first compact deflecting and crabbing geometry that has demonstrated high gradients and high shunt impedance. Since the fundamental operating mode is the lowest mode and is widely separated from the nearest higher order mode, the rf-dipole design is an attractive geometry for effective damping of the higher order modes in high current applications. A 400 MHz rf-dipole cavity has been designed, fabricated, and tested as a proof-of-principle cavity. The cavity achieved high operating gradients, and the multipacting levels were easily processed and did not reoccur.

43 PARTICLE ACCELERATORS↗
DOE OSTI2018

Coupled Bunch Instability from JLEIC Crab Cavity Higher Order Modes

Particle bunches traveling in a ring can excite wakefields inside any radio-frequency (rf) element present. These electromagnetic modes can resonate long enough and interact with subsequent passing bunches. A coherent oscillation between bunches can quickly become an instability and needs to be addressed. The Jefferson Lab Electron-Ion Collider (JLEIC) has a large 50 mrad crossing angle and thus relies on bunch crabbing to achieve high luminosity. Bunch crabbing is done with compact superconducting rf dipole cavities. We study coupled bunch oscillations driven by the higher order modes (HOM) of multi-cell rf dipole (rfd) crab cavities under study for JLEIC, we calculate the instability growth time assuming a symmetric beam frequency spectrum, identify the HOM driving the instability and discuss mitigation measures.

Sosa Guitron, Salvador I.↗
DOE OSTI2022

Design of a 1.3 GHz RF-Dipole Crabbing Cavity for International Linear Collider

The International Liner Collider (ILC) requires crabbing systems to increase the luminosity of the colliding electron and positron bunches. There are several frequency options for the crabbing cavity. We have designed a 1.3 GHz compact 1-cell and 2-cell rf-dipole crabbing cavity to compensate for luminosity degradation due to large crossing angle. This paper presents the 1-cell and 2-cell cavities designed to meet the current specifications including the fundamental power coupler and higher order mode couplers.

De Silva, S.U.↗
DOE OSTI2022

TOLERANCES OF CRAB DISPERSION AT THE INTERACTION POINT IN THE HADRON STORAGE RING OF THE ELECTRON-ION COLLIDER

The Electron Ion Collider (EIC) presently under construction at Brookhaven National Laboratory will collide polarized high energy electron beams with hadron beams with luminosities up to 10^34 cm^?2 s^?1 in the center mass energy range of 20-140 GeV. Due to the detector solenoid in the interaction region, the design horizontal crabbing angle will be coupled to the vertical plane if uncompensated. In this article, we study the tolerances of crab dispersion at the interaction point in the EIC Hadron Storage Ring (HSR). Both strong-strong and weak-strong simulations are used. We found that there is a tight tolerance of vertical crabbing angle at the interaction point in the HSR.

Luo, Y.↗
DOE OSTI2022

6-D ELEMENT-BY-ELEMENT PARTICLE TRACKING WITH CRAB CAVITY PHASE NOISE AND WEAK-STRONG BEAM-BEAM INTERACTION FOR THE HADRON STORAGE RING OF THE ELECTRON-ION COLLIDER

The Electron Ion Collider (EIC) presently under construction at Brookhaven National Laboratory will collide polarized high energy electron beams with hadron beams with luminosities up to 10^34 cm?^2 s^?1 in center mass energy range of 20-140 GeV. Crab cavities are used to compensate the geometric luminosity due to a large crossing angle 25 mrad in the EIC. It was found that the phase noise in crab cavities will generate a significant emittance growth for the hadron beams. The phase noise tolerance from the analytical calculation is very small for the Hadron Storage Ring (HSR) of the EIC. In this article, we present our preliminary numerical simulation results with a 6-d symplectic particle tracking to determine the proton emittance growth rate with crab cavity phase noise and beam-beam interaction for the HSR.

Luo, Y.↗
DOE OSTI2014

Double Quarter Wave Crab Cavity Field Profile Analysis and Higher Order Mode Characterization

The Large Hadron Collider (LHC) is underway for a major upgrade to increase its luminosity by an order of magnitude beyond its original design specifications. This novel machine configuration known as the High Luminosity LHC (HL-LHC) will rely on various innovative technologies including very compact and ultra-precise superconducting crab cavities for beam rotation. A double quarter wave crab cavity (DQWCC) has been designed at Brookhaven National Laboratory for the HL-LHC. This cavity as well as the structural support components were fabricated and assembled at Niowave. The field profile of the crabbing mode for the DQWCC was investigated using a phase shift bead pulling technique and compared with simulated results to ensure proper operation or discover discrepancies from modeled results and/or variation in fabrication tolerances. Higher-Order Mode (HOM) characterization was also performed and correlated with simulations.

43 PARTICLE ACCELERATORS↗
DOE OSTI2021

Instabilities driven by the fundamental crabbing mode

The Electron Ion Collider (EIC) requires crab cavities to correct for crossing angle effects. These cavities produce a time varying horizontal kick that makes the collision head on in the center of mass frame of the bunches. This results in a luminosity that is very close to the the luminosity obtained without a crossing angle. Producing the kick requires a transverse RF field. This field requires a superconducting resonator and reasonable power levels require loaded quality factors of order a million. This results is a very large transverse impedance for the crabbing mode. The horizontal beta function is large and this, coupled with the large transverse impedance of the resonator can lead to strong instabilities. In the first section of the paper a simple model is used to describe the situation without feedback. There are large ranges of tune leading to strong instabilities in both the electron and hadron storage rings of the EIC. These estimates are confirmed with simulations. In the second section, RF feedback is used to reduce the apparent impedance of the crabbing mode. Simulating the actual feedback would require both a significant rewrite of the tracking code and a significant reduction in computational speed. Instead, the apparent impedance is fitted using one pole filters, which allows use of the existing simulation code. In the third section a transverse damping system is outlined.

43 PARTICLE ACCELERATORS↗
DOE OSTI2022

TOLERANCES OF CRAB DISPERSION AT THE INTERACTION POINT IN THE HADRON STORAGE RING OF THE ELECTRON-ION COLLIDER

The Electron Ion Collider (EIC) presently under construction at Brookhaven National Laboratory will collide polarized high energy electron beams with hadron beams with luminosities up to 10^34 cm^?2 s^?1 in the center mass energy range of 20-140 GeV. Due to the detector solenoid in the interaction region, the design horizontal crabbing angle will be coupled to the vertical plane if uncompensated. In this article, we study the tolerances of crab dispersion at the interaction point in the EIC Hadron Storage Ring (HSR). Both strong-strong and weak-strong simulations are used. We found that there is a tight tolerance of vertical crabbing angle at the interaction point in the HSR.

Luo, Y.↗
DOE OSTI2024

Crabbing Angle Measurement

Electron-ion collider will employ transverse deflecting (crabbing) cavities to increase luminosity. There will be multiple cavities which will create localized crab bump in the interaction region. For proper compensation of the crossing angle each crab cavity should individually calibrated and phased.

43 PARTICLE ACCELERATORS↗
DOE OSTI2025

EIC Crab Cavity LLRF Studies

The Electron-Ion Collider Crab Cavity Low-Level Radio Frequency system will have to reduce the Crab Cavity impedance to prevent transverse instabilities, while regulating the crabbing voltage and minimizing the Radio Frequency noise levels injected to the beam. These are challenging and partly conflicting requirements. This works summarizes the specifications to achieve these requirements and investigates the possible trade-offs in the architecture.

43 PARTICLE ACCELERATORS↗