High-power, relativistic electron beams from energy-recovering linacs have great potential to realize new experimental paradigms for pioneering innovation in fundamental and applied research. A major ...design consideration for this new generation of experimental capabilities is the understanding of the halo associated with these bright, intense beams. In this Letter, we report on measurements performed using the 100 MeV, 430 kW cw electron beam from the energy-recovering linac at the Jefferson Laboratory's Free Electron Laser facility as it traversed a set of small apertures in a 127 mm long aluminum block. Thermal measurements of the block together with neutron measurements near the beam-target interaction point yielded a consistent understanding of the beam losses. These were determined to be 3 ppm through a 2 mm diameter aperture and were maintained during a 7 h continuous run.
PMT signal increase using a wavelength shifting paint Allada, K.; Hurlbut, Ch; Ou, L. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
05/2015, Letnik:
782, Številka:
C
Journal Article
Recenzirano
Odprti dostop
We report a 1.65 times increase of the PMT signal and a simple procedure of application of a new wavelength shifting (WLS) paint for PMTs with non-UV-transparent windows. Samples of four different ...WLS paints, made from hydrocarbon polymers and organic fluors, were tested on a 5-in. PMT (ET 9390KB) using Cherenkov radiation produced in fused silica disks by 106Ru electrons on a ‘table-top’ setup. The best performing paint was employed on two different types of 5-in. PMTs (ET 9390KB and XP4572B), installed in atmospheric pressure CO2 gas Cherenkov detectors, and tested using GeV electrons.
Transmission of high-power electron beams through small apertures Tschalär, C.; Alarcon, R.; Balascuta, S. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/2013, Letnik:
729
Journal Article
Recenzirano
Odprti dostop
Tests were performed to pass a 100MeV, 430kWatt c.w. electron beam from the energy-recovery linac at the Jefferson Laboratory's FEL facility through a set of small apertures in a 127mm long aluminum ...block. Beam transmission losses of 3p.p.m. through a 2mm diameter aperture were maintained during a 7h continuous run.
We report measurements of photon and neutron radiation levels observed while transmitting a 0.43MW electron beam through millimeter-sized apertures and during beam-off, but accelerating gradient ...RF-on, operation. These measurements were conducted at the Free-Electron Laser (FEL) facility of the Jefferson National Accelerator Laboratory (JLab) using a 100mev electron beam from an energy-recovery linear accelerator. The beam was directed successively through 6mm, 4mm, and 2mm diameter apertures of length 127mm in aluminum at a maximum current of 4.3mA (430kW beam power). This study was conducted to characterize radiation levels for experiments that need to operate in this environment, such as the proposed DarkLight Experiment. We find that sustained transmission of a 430kW continuous-wave (CW) beam through a 2mm aperture is feasible with manageable beam-related backgrounds. We also find that during beam-off, RF-on operation, multipactoring inside the niobium cavities of the accelerator cryomodules is the primary source of ambient radiation when the machine is tuned for 130mev operation.
The first measurement of lepton-jet momentum imbalance and azimuthal correlation in lepton-proton scattering at high momentum transfer is presented. These data, taken with the H1 detector at HERA, ...are corrected for detector effects using an unbinned machine learning algorithm (multifold), which considers eight observables simultaneously in this first application. The unfolded cross sections are compared with calculations performed within the context of collinear or transverse-momentum-dependent factorization in quantum chromodynamics as well as Monte Carlo event generators.
This White Paper aims at highlighting the important benefits in the science reach of the EIC. High luminosity operation is generally desirable, as it enables producing and harvesting scientific ...results in a shorter time period. It becomes crucial for programs that would require many months or even years of operation at lower luminosity.
Short-range correlated (SRC) nucleon pairs are a vital part of the nucleus, accounting for almost all nucleons with momentum greater than the Fermi momentum (k_{F}). A fundamental characteristic of ...SRC pairs is having large relative momenta as compared to k_{F}, and smaller center of mass (c.m.) which indicates a small separation distance between the nucleons in the pair. Determining the c.m. momentum distribution of SRC pairs is essential for understanding their formation process. We report here on the extraction of the c.m. motion of proton-proton (pp) SRC pairs in carbon and, for the first time in heavier and ansymetric nuclei: aluminum, iron, and lead, from measurements of the A(e,e^{'}pp) reaction. We find that the pair c.m. motion for these nuclei can be described by a three-dimensional Gaussian with a narrow width ranging from 140 to 170 MeV/c, approximately consistent with the sum of two mean-field nucleon momenta. Comparison with calculations appears to show that the SRC pairs are formed from mean-field nucleons in specific quantum states.
Charged particle multiplicity distributions in positron-proton deep inelastic scattering at a centre-of-mass energy
s
=
319
GeV are measured. The data are collected with the H1 detector at HERA ...corresponding to an integrated luminosity of 136 pb
-
1
. Charged particle multiplicities are measured as a function of photon virtuality
Q
2
, inelasticity
y
and pseudorapidity
η
in the laboratory and the hadronic centre-of-mass frames. Predictions from different Monte Carlo models are compared to the data. The first and second moments of the multiplicity distributions are determined and the KNO scaling behaviour is investigated. The multiplicity distributions as a function of
Q
2
and the Bjorken variable
x
bj
are converted to the hadron entropy
S
hadron
, and predictions from a quantum entanglement model are tested.
The HERAPDF2.0 ensemble of parton distribution functions (PDFs) was introduced in 2015. The final stage is presented, a next-to-next-to-leading-order (NNLO) analysis of the HERA data on inclusive ...deep inelastic
ep
scattering together with jet data as published by the H1 and ZEUS collaborations. A perturbative QCD fit, simultaneously of
α
s
(
M
Z
2
)
and the PDFs, was performed with the result
α
s
(
M
Z
2
)
=
0.1156
±
0.0011
(
exp
)
-
0.0002
+
0.0001
(
model
+
parameterisation
)
±
0.0029
(
scale
)
. The PDF sets of HERAPDF2.0Jets NNLO were determined with separate fits using two fixed values of
α
s
(
M
Z
2
)
,
α
s
(
M
Z
2
)
=
0.1155
and 0.118, since the latter value was already chosen for the published HERAPDF2.0 NNLO analysis based on HERA inclusive DIS data only. The different sets of PDFs are presented, evaluated and compared. The consistency of the PDFs determined with and without the jet data demonstrates the consistency of HERA inclusive and jet-production cross-section data. The inclusion of the jet data reduced the uncertainty on the gluon PDF. Predictions based on the PDFs of HERAPDF2.0Jets NNLO give an excellent description of the jet-production data used as input.
PDF
