A hybrid readout Time Projection Chamber (TPC) has a simultaneous optical- and charge readout. The optical readout provides 2D images of particle tracks in the active volume, whilst the charge ...readout provides additional information on the particle position perpendicular to the image plane. A hybrid readout TPC working at high pressure is an attractive device for physics cases where an excellent space point resolution and a high target density is required as
e.g.
measuring a neutrino beam at the source of a long baseline neutrino oscillation experiment. In this paper we present two different lines of work towards the goal of developing hybrid TPC technology: a) Commissioning of a set-up with gas electron multipliers employing optical and charge readout. b) An analytical parametrisation of the gas gain for a multi wire proportional chamber based on GARFIELD++ simulations, which – when validated with measurements – allows to skip these simulations in the future altogether.
New neutrino–nucleus interaction cross-section measurements are required to improve nuclear models sufficiently for future long baseline neutrino experiments to meet their sensitivity goals. A time ...projection chamber (TPC) filled with a high-pressure gas is a promising detector to characterise the neutrino sources used for such experiments. A gas-filled TPC is ideal for measuring low-energy particles, which travel further in gas than in solid or liquid detectors and using high-pressure increases the target density, resulting in more neutrino interactions. We examine the suitability of multiwire proportional chambers (MWPCs) from the ALICE TPC for use as the readout chambers of a high-pressure gas TPC. These chambers were previously operated at atmospheric pressure. We report the successful operation of an ALICE TPC outer readout chamber (OROC) at pressures up to 4.2 bar absolute (barA) with
Ar-CH
4
mixtures with a
CH
4
content between 2.8 and 5.0%, and so far up to 4 bar absolute with
Ar-CO
2
(90-10). The charge gain of the OROC was measured with signals induced by an
55
Fe
source. The largest gain achieved at 4.2 bar was
(
29
±
1
)
·
10
3
in
Ar-CH
4
with 4.0%
CH
4
with an anode voltage of
2975
V
. In
Ar-CO
2
with 10%
CO
2
at 4 barA, a gain of
(
4.2
±
0.1
)
·
10
3
was observed with anode voltage
2975
V
. We extrapolate that at 10 barA, an interesting pressure for future neutrino experiments, a gain of 5000 in
Ar-CO
2
with 10%
CO
2
(10,000 in
Ar-CH
4
with
∼
4
%
CH
4
) may be achieved with anode voltage of
4.6
kV
(
∼
3.6
kV
).
Secondary discharge studies in single- and multi-GEM structures Deisting, A.; Garabatos, C.; Gasik, P. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
09/2019, Letnik:
937
Journal Article
Recenzirano
Odprti dostop
Secondary discharges, which consist of the breakdown of a gap near a GEM foil upon a primary discharge across that GEM, are studied in this work.
Their main characteristics are the occurrence a few ...10μs after the primary, the relatively sharp onset at moderate electric fields across the gap, the absence of increased fields in the system, and their occurrence under both field directions.
They can be mitigated using series resistors in the high-voltage connection to the GEM electrode facing towards an anode. The electric field at which the onset of secondary discharges occurs indeed increases with increasing resistance. Discharge propagation from GEM to GEM in a multi-GEM system affects the occurrence probability of secondary discharges in the gaps between neighbouring GEMs.
Furthermore, evidence of charges flowing through the gap after the primary discharge are reported. Such currents may or may not lead to a secondary discharge. A characteristic charge, of the order of 1010 electrons, has been measured as the threshold for a primary discharge to be followed by a secondary discharge, and this number slightly depends on the gas composition. A mechanism involving the heating of the cathode surface as trigger for secondary discharges is proposed.
The World Health Organisation (WHO) presents an upper limit for lead in drinking water of 10 parts per billion ppb. Typically, to reach this level of sensitivity, expensive metrology is required. To ...increase the sensitivity range of low-cost devices, this paper explores the prospects of using a volume reduction technique of a boiled water sample doped with Lead-210 (
210
Pb), as a means to increase the solute’s concentration.
210
Pb is a radioactive lead isotope and its concentration in a water sample can be measured with e.g. High Purity Germanium (HPGe) detectors at the Boulby Underground Germanium Suite. Concentrations close to the WHO limit have not been examined. This paper presents a measurement of the volume reduction technique retaining
99
±
(
9
)
% of
210
Pb starting from a concentration of
1.9
×
10
-
6
ppb before reduction and resulting in
2.63
×
10
-
4
ppb after reduction. This work also applies the volume reduction technique to London tap water and reports the radioassay results from gamma counting in HPGe detectors. Among other radio-isotopes,
40
K,
210
Pb,
131
I and
177
Lu were identified at measured concentrations of
2.83
×
10
3
ppb,
2.55
×
10
-
7
ppb,
5.06
×
10
-
10
ppb and
5.84
×
10
-
10
ppb in the London tap water sample. This technique retained
90
±
50
%
of
40
K. Stable lead was inferred from the same water sample at a measured concentration of 0.012 ppb, prior to reduction.
The
γ
-ray flux inside
La Guadalupe
mine, the selected site for the construction of the underground laboratory LABChico in Mexico, is reported for energies below 3 MeV. Data were recorded with a ...0.669 kg thallium-activated sodium iodide (NaI) crystal detector deployed for 3.6 hr. The detector response was calculated via Monte Carlo simulations with GEANT4 and validated against point-like calibration sources, and the
γ
-ray spectrum was extracted using an unfolding technique. The
γ
-ray flux above 250 keV and below 3 MeV is 0.1768
γ
/cm
2
/s. The two most intense
γ
-rays in the natural radioactive background,
40
K and
208
Tl, were identified. The flux measured for these isotopes is 0.0363 ± 0.0020
γ
/cm
2
/s and 0.0016 ± 0.0005
γ
/cm
2
/s, respectively. A
γ
-ray spectrometry analysis of rock samples showed 674.0 ± 2.0 Bq/kg, 24.0 ± 0.1 Bq/kg, and 17.7 ± 0.2 Bq/kg, of
40
K,
232
Th, and
238
U, respectively. These results are compared with deep underground facilities such as SURF, SNOLAB, Boulby, Modane, and Gran Sasso, with differences observed mainly due to the rock composition. Geotechnical studies of the mine and its rock composition are also reported.
We present studies of proton fluxes in the T10 beamline at CERN. A prototype high pressure gas time projection chamber (TPC) was exposed to the beam of protons and other particles, using the 0.8 ...GeV/c momentum setting in T10, in order to make cross section measurements of low energy protons in argon. To explore the energy region comparable to hadrons produced by GeV-scale neutrino interactions at oscillation experiments, i.e., near 0.1 GeV of kinetic energy, methods of moderating the T10 beam were employed: the dual technique of moderating the beam with acrylic blocks and measuring scattered protons off the beam axis was used to decrease the kinetic energy of incident protons, as well as change the proton/minimum ionising particle (MIP) composition of the incident flux. Measurements of the beam properties were made using time of flight systems upstream and downstream of the TPC. The kinetic energy of protons reaching the TPC was successfully changed from ∼0.3 GeV without moderator blocks to less than 0.1 GeV with four moderator blocks (40 cm path length). The flux of both protons and MIPs off the beam axis was increased. The ratio of protons to MIPs vary as a function of the off-axis angle allowing for possible optimisation of the detector to select the type of required particles. Simulation informed by the time of flight measurements show that with four moderator blocks placed in the beamline, (5.6 ± 0.1) protons with energies below 0.1 GeV per spill traversed the active TPC region. Measurements of the beam composition and energy are presented.
Abstract New neutrino–nucleus interaction cross-section measurements are required to improve nuclear models sufficiently for future long baseline neutrino experiments to meet their sensitivity goals. ...A time projection chamber (TPC) filled with a high-pressure gas is a promising detector to characterise the neutrino sources used for such experiments. A gas-filled TPC is ideal for measuring low-energy particles, which travel further in gas than in solid or liquid detectors and using high-pressure increases the target density, resulting in more neutrino interactions. We examine the suitability of multiwire proportional chambers (MWPCs) from the ALICE TPC for use as the readout chambers of a high-pressure gas TPC. These chambers were previously operated at atmospheric pressure. We report the successful operation of an ALICE TPC outer readout chamber (OROC) at pressures up to 4.2 bar absolute (barA) with $$\text {Ar-CH}_4$$ Ar-CH 4 mixtures with a $$\text {CH}_{4}$$ CH 4 content between 2.8 and 5.0%, and so far up to 4 bar absolute with $${\text {Ar-CO}}_2$$ Ar-CO 2 (90-10). The charge gain of the OROC was measured with signals induced by an $$^{55}\text {Fe}$$ 55 Fe source. The largest gain achieved at 4.2 bar was $$(29\pm 1)\cdot 10^{3}$$ ( 29 ± 1 ) · 10 3 in $$\text {Ar-CH}_4$$ Ar-CH 4 with 4.0% $$\text {CH}_{4}$$ CH 4 with an anode voltage of $${2975}\,\hbox {V}$$ 2975 V . In $${\text {Ar-CO}}_2$$ Ar-CO 2 with 10% $$\text {CO}_{2}$$ CO 2 at 4 barA, a gain of $$(4.2\pm 0.1)\cdot 10^{3}$$ ( 4.2 ± 0.1 ) · 10 3 was observed with anode voltage $${2975}\,\hbox {V}$$ 2975 V . We extrapolate that at 10 barA, an interesting pressure for future neutrino experiments, a gain of 5000 in $${\text {Ar-CO}}_2$$ Ar-CO 2 with 10% $$\text {CO}_{2}$$ CO 2 (10,000 in $$\text {Ar-CH}_4$$ Ar-CH 4 with $$\sim \!{4}{\%}$$ ∼ 4 % $$\text {CH}_{4}$$ CH 4 ) may be achieved with anode voltage of $${4.6}\,\hbox {kV}$$ 4.6 kV ( $$\sim \!{3.6}\,\hbox {kV}$$ ∼ 3.6 kV ).
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