110357550
Specialized Technical Services at ESS
The European Spallation Source (ESS), a world class lab for neutron science currently under construction in Lund, Sweden requires a number of technical services that extend across the various project areas (accelerator, target and neutron science). These services include: cryogenics, vacuum and technical electrical and cooling systems. This effort constitutes more than 70 million Euros of construction cost. Rather than have separate support groups in each of the project areas, ESS has created a Specialized Technical Services group within the Accelerator Division to provide these services. This approach permits standardization, development of synergies and improved communication. The STS group also provides cryomodule testing to the accelerator project. This paper describes the scope of work, current design status and future plans for Specialized Technical services at ESS.
54894329
The ESS Cryogenic System
The European Spallation Source (ESS) is a neutron science facility funded by a collaboration of 17 European countries currently under design and construction in Lund, Sweden. Cryogenic cooling is vital for large sections at ESS. Mainly there is a 2.0 GeV proton linac using superconducting RF cavities operating at 2 K. In addition to cooling the SRF cavities, cryogenics is also used for the cold hydrogen moderator surrounding the target. ESS furthermore uses both liquid helium and liquid nitrogen in a number of the neutron instruments. There is also a cryogenic installation associated with the site acceptance testing of the ESS cryomodules [1]. This paper describes the conceptual design of the ESS cryogenic system including the expected heat loads and cryoplant features. Challenges associated with the required high reliability and turn-down capability will also be discussed.
120435997
High-pT hadronic trigger using electromagnetic calorimeter with the STAR detector
Abstract We derive a new method to improve the statistics of identified particles at high transverse momentum ( p T ) using online-triggered events by the STAR Barrel electro-magnetic-calorimeter (BEMC) detector. The BEMC is used to select charged hadrons ( π ± , K ± , and p ( p ¯ ) ) via hadronic shower energy deposited in the BEMC. With this trigger, the statistics of the high p T particles are significantly enhanced (by a factor of up to ∼ 100 for STAR) with trigger efficiency up to 20%. In addition, weak-decay V0s ( K S 0 and Λ ( Λ ¯ ) ) can be reconstructed by selecting the BEMC-trigger hadron as one of the decay daughters. We also show that the trigger efficiency can be obtained reliably in simulation and data-driven approaches, and final results from new method are compared with previous published results.
119093501
Investigation of target in C-ADS and IAEA ADS benchmark
The spatial and energy distribution of spallation neutrons have an effect on the performance of Accelerator Driven Subcritical systems. In this work, the spatial, energy distribution of spallation neutrons and the effect of these factors on proton efficiency was studied. When the radius of spallation region increases, backward neutrons were found to have a rather big ratio and have a positive effect on proton efficiency. By making better use of these neutrons, we may increase the radius of target to satisfy some other requirements in the design of subcritical core.
118559274
Spin-Orbit Interaction of Nuclear Shell Structure
Single particle spin-orbit interaction energy problem in nuclear shell structure is solved through negative harmonic oscillator in the self-similar-structure shell model (SSM) [4] and considering quarks' contributions on single particle spin and orbit momentum. The paper demonstrates that single particle motion in normal nuclei is described better by SSM negative harmonic oscillator than conventional shell model positive harmonic oscillator[1][2][3]. The proposed theoretical formula for spin orbit interaction energy agrees well to experiment measurements.
55046954
Berkeley Supernova Ia Program - I. Observations, data reduction and spectroscopic sample of 582 low-redshift Type Ia supernovae
In this first paper in a series, we present 1298 low-redshift (z ≲ 0.2) optical spectra of 582 Type Ia supernovae (SNe Ia) observed from 1989 to 2008 as part of the Berkeley Supernova Ia Program (BSNIP). 584 spectra of 199 SNe Ia have well-calibrated light curves with measured distance moduli, and many of the spectra have been corrected for host-galaxy contamination. Most of the data were obtained using the Kast double spectrograph mounted on the Shane 3 m telescope at Lick Observatory and have a typical wavelength range of 3300–10 400 A, roughly twice as wide as spectra from most previously published data sets. We present our observing and reduction procedures, and we describe the resulting SN Database, which will be an online, public, searchable data base containing all of our fully reduced spectra and companion photometry. In addition, we discuss our spectral classification scheme (using the SuperNova IDentification code, snid; Blondin & Tonry), utilizing our newly constructed set of snid spectral templates. These templates allow us to accurately classify our entire data set, and by doing so we are able to reclassify a handful of objects as bona fide SNe Ia and a few other objects as members of some of the peculiar SN Ia subtypes. In fact, our data set includes spectra of nearly 90 spectroscopically peculiar SNe Ia. We also present spectroscopic host-galaxy redshifts of some SNe Ia where these values were previously unknown. The sheer size of the BSNIP data set and the consistency of our observation and reduction methods make this sample unique among all other published SN Ia data sets and complementary in many ways to the large, low-redshift SN Ia spectra presented by Matheson et al. and Blondin et al. In other BSNIP papers in this series, we use these data to examine the relationships between spectroscopic characteristics and various observables such as photometric and host-galaxy properties.
64627689
The progress of development of four kickers' bump system for injection in HLS ring
There are three kicker magnets to manipulate local bump orbit in Hefei storage ring, which could satisfy basically the commissioning and operations of General Purpose Light Source (GPLS) mode. In the Phase Two Project of HLS, four kicker magnets will be employed and installed in one straight section to form a ladder-shaped bump orbit. So the parameters of bump orbit are independent of the ring lattice. The new system also satisfies the multicycle and multiturn injection of High Brightness Light Source (HBLS) mode and other modes, and it expected to run stably for a long time. This paper presents the development of the new bump orbit system.