The unprecedented intensity of x-ray free-electron laser sources has enabled single-particle x-ray diffraction imaging (SPI) of various biological specimens in both two-dimensional projection and ...three dimensions (3D). The potential of studying protein dynamics in their native conditions, without crystallization or chemical staining, has encouraged researchers to aim for increasingly higher resolutions with this technique. The currently achievable resolution of SPI is limited to the sub-10 nanometer range, mainly due to background effects, such as instrumental noise and parasitic scattering from the carrier gas used for sample delivery. Recent theoretical studies have quantified the effects of x-ray pulse parameters, as well as the required number of diffraction patterns to achieve a certain resolution, in a 3D reconstruction, although the effects of detector noise and the random particle orientation in each diffraction snapshot were not taken into account. In this work, we show these shortcomings and address limitations on achievable image resolution imposed by the adaptive gain integrating pixel detector noise.
A MHz frame rate X-ray area detector (LPD - Large Pixel Detector) is under development by the Rutherford Appleton Laboratory for the European XFEL. The detector will have 1 million pixels and allows ...analogue storage of 512 images taken at 4.5 MHz in the detector front end. The LPD detector has 500 mu m thick silicon sensor tiles that are bump bonded to a readout ASIC. The ASIC's preamplifier provides relatively low noise at high speed which results in a high dynamic range of 10 super(5) photons over an energy range of 5-20 keV. Small scale prototypes of 32 x 256 pixels (LPD 2-Tile detector) and 256 x 256 pixels (LPD supermodule detector) are now available for X-ray tests. The performance of prototypes of the detector is reported for first tests under synchrotron radiation (PETRA III at DESY) and Free-Electron-Laser radiation (LCLS at SLAC). The initial performance of the detector in terms of signal range and noise, radiation hardness and spatial and temporal response are reported. The main result is that the 4.5 MHz sampling detection chain is reliably working, including the analogue on-chip memory concept. The detector is at least radiation hard up to 5 MGy at 12 keV. In addition the multiple gain concept has been demonstrated over a dynamic range to 10 super(4) at 12 keV with a readout noise equivalent to <1 photon rms in its most sensitive mode.
Measurement of the luminosity in the ZEUS experiment at HERA II Adamczyk, L.; Andruszkow, J.; Bold, T. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2014, Volume:
744
Journal Article
Peer reviewed
Open access
The luminosity in the ZEUS detector was measured using photons from electron bremsstrahlung off protons. In 2001 the HERA collider was upgraded for operation at higher luminosity. At the same time ...the luminosity-measuring system of the ZEUS experiment was modified to tackle the expected higher photon rate and synchrotron radiation. The existing lead-scintillator calorimeter was equipped with radiation hard scintillator tiles and shielded against synchrotron radiation. In addition, a magnetic spectrometer was installed to measure the luminosity independently using photons converted in the beam-pipe exit window. The redundancy provided a reliable and robust luminosity determination with a systematic uncertainty of 1.7%. The experimental setup, the techniques used for luminosity determination and the estimate of the systematic uncertainty are reported.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The European XFEL is establishing cooperation with the Paul Scherrer Institute in Villigen to develop a new version of the Gotthard detector best suited to the European XFEL needs. The use case and ...the required detector specifications are illustrated. Starting from the present detector version, the modifications planned to adapt it to the European XFEL running conditions are described. In another particular application, resonant inelastic X-ray scattering, a Micro-Channel Plate detector matched to a delay-line readout is foreseen to be used. In this case the European XFEL is aiming for a highly customized solution provided by the German company Surface Concept. The use case is described, the science-driven detector specifications are illustrated and the expected detector performance is shown.
The exclusive electroproduction of
J/
ψ mesons,
ep→
epJ/
ψ, has been studied with the ZEUS detector at HERA for virtualities of the exchanged photon in the ranges
0.15<Q
2<0.8
GeV
2
and
2<Q
2<100
GeV
...2
using integrated luminosities of 69 and
83
pb
−1
, respectively. The photon–proton centre-of-mass energy was in the range
30<W<220
GeV
and the squared four-momentum transfer at the proton vertex
|t|<1
GeV
2
. The cross sections and decay angular distributions are presented as functions of
Q
2,
W and
t. The effective parameters of the pomeron trajectory are in agreement with those found in
J/
ψ photoproduction. The spin-density matrix elements, calculated from the decay angular distributions, are consistent with the hypothesis of
s-channel helicity conservation. The ratio of the longitudinal to transverse cross sections,
σ
L
/
σ
T
, grows with
Q
2, whilst no dependence on
W or
t is observed. The results are in agreement with perturbative QCD calculations and exhibit a strong sensitivity to the gluon distribution in the proton.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The ZEUS inclusive differential cross-section data from HERA, for charged and neutral current processes taken with e + and e- beams, together with differential cross-section data on inclusive jet ...production in e + p scattering and dijet production in \(\gamma p\) scattering, have been used in a new NLO QCD analysis to extract the parton distribution functions of the proton. The input of jet-production data constrains the gluon and allows an accurate extraction of \(\alpha_s(M_Z)\) at NLO; \(\alpha _{s} {\left( {M_{Z} } \right)} = 0.1183 \pm 0.0028{\left( {\exp .} \right)} \pm 0.0008{\left( {{\text{model}}} \right)}.\) An additional uncertainty from the choice of scales is estimated as \(\pm 0.005\). This is the first extraction of \(\alpha_s(M_Z)\) from HERA data alone.
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DOBA, FZAB, GEOZS, IJS, IMTLJ, IZUM, KILJ, KISLJ, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Exclusive electroproduction of
ϕ mesons has been studied in
e
±
p
collisions at
s
=
318
GeV
with the ZEUS detector at HERA using an integrated luminosity of
65.1
pb
−1
. The
γ
∗
p
cross section ...is presented in the kinematic range
2
GeV
2
<
Q
2
<
70
GeV
2
,
35
GeV
<
W
<
145
GeV
and
|
t
|
<
0.6
GeV
2
. The cross sections as functions of
Q
2
,
W,
t and helicity angle
θ
h
are compared to cross sections for other vector mesons. The ratios
R of the cross sections for longitudinally and transversely polarized virtual photons are presented as functions of
Q
2
and
W. The data are also compared to predictions from theoretical models.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Deep inelastic scattering and its diffractive component,
e
p
→
e
′
γ
∗
p
→
e
′
X
N
, have been studied at HERA with the ZEUS detector using an integrated luminosity of
4.2
pb
−1
. The measurement ...covers a wide range in the
γ
∗
p
c.m. energy
W (37–245 GeV), photon virtuality
Q
2 (2.2–80 GeV
2) and mass
M
X
(0.28–35 GeV). The diffractive cross section for
M
X
>
2
GeV
rises strongly with
W; the rise is steeper with increasing
Q
2. The latter observation excludes the description of diffractive deep inelastic scattering in terms of the exchange of a single pomeron. The ratio of diffractive to total cross section is constant as a function of
W, in contradiction to the expectation of Regge phenomenology combined with a naive extension of the optical theorem to
γ
∗
p
scattering. Above
M
X
of 8 GeV, the ratio is flat with
Q
2, indicating a leading-twist behaviour of the diffractive cross section. The data are also presented in terms of the diffractive structure function,
F
2
D
(
3
)
(
β
,
x
P
,
Q
2
)
, of the proton. For fixed
β, the
Q
2 dependence of
x
P
F
2
D
(
3
)
changes with
x
P
in violation of Regge factorisation. For fixed
x
P
,
x
P
F
2
D
(
3
)
rises as
β
→
0
, the rise accelerating with increasing
Q
2. These positive scaling violations suggest substantial contributions of perturbative effects in the diffractive DIS cross section.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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