Status of the SPARC project Alesini, D; Bertolucci, S; Biagini, M.E ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/2004, Letnik:
528, Številka:
1
Journal Article
Recenzirano
In this paper we report on the final design of the SPARC FEL experiment which is under construction at the Frascati INFN Laboratories by a collaboration between INFN, ENEA, ELETTRA, Un. of Rome (Tor ...Vergata), CNR and INFM. This project comprises an advanced 150
MeV photo-injector aimed at producing a high brightness electron beams to drive a SASE-FEL experiment in the visible using a segmented 12
m long undulator. The project, finally approved and funded early this year, has a 3 year time span, with the final goal of reaching saturation on the fundamental of the SASE-FEL and studying the resonant non-linear generation of harmonics. Peculiar features of this project are the optimized design of the photo-injector to reach minimum emittances by using flat-top laser pulses on the photocathode, and the use of an uncompressed electron beam of 100
A peak current at very low emittance to drive the FEL. Results of start-to-end simulations carried out to optimize the performances of the whole system are presented, as well as the status of the construction and assembly of the system components. Activities planned for a second phase of the project are also mentioned: these are mainly focused on velocity bunching experiments that will be conducted with the aim to reach higher peak currents with preservation of low transverse emittances.
The Σ beam asymmetry for positive pion photoproduction on the proton has been measured over an angular range of 40–170° at photon energies from 0.8 to 1.5 GeV. The resulting data set includes 237 ...accurate points, 136 of these belonging to an almost unexplored domain above 1.05 GeV. Data of such high precision provide severe constraints for partial wave analyses. The influence of this experiment on the GW multipole analysis is demonstrated. Significant changes are found in multipoles connected to the S31(1620) and P13(1720) resonances. Comparisons using the MAID analysis are also presented.
We have studied the vector to pseudoscalar conversion decay ϕ→ηe+e−, with η→π0π0π0, with the KLOE detector at DAΦNE. The data set of 1.7 fb−1 of e+e− collisions at s∼Mϕ contains a clear conversion ...decay signal of ∼31,000 events from which we measured a value of BR(ϕ→ηe+e−)=(1.075±0.007±0.038)×10−4. The same sample is used to determine the transition form factor by a fit to the e+e− invariant mass spectrum, obtaining bϕη=(1.28±0.10−0.08+0.09) GeV−2, that improves by a factor of five the precision of the previous measurement and is in good agreement with VMD expectations.
The differential cross section for the quasi-free photoproduction reaction
γ
n
→
K
0
Σ
0
was measured at BGOOD at ELSA from threshold to a centre-of-mass energy of
2400
MeV
. Close to threshold the ...results are consistent with existing data and are in agreement with partial wave analysis solutions over the full measured energy range, with a large coupling to the
Δ
(
1900
)
1
/
2
-
evident. This is the first dataset covering the
K
∗
threshold region, where there are model predictions of dynamically generated vector meson-baryon resonance contributions.
Ricotta salata is a whey protein cheese produced in Sardinia that in the last decades has been linked to several recalls and in 2012 to a severe human listeriosis outbreak. Contamination of ricotta ...salata with Listeria monocytogenes mainly occurs during post-process handling and generally origins from the processing environment. The application of water bath heat treatment in vacuum packed ricotta salata is a possible strategy to control L. monocytogenes superficial contamination. The objective of the present study was to select a heat treatment able to inactivate L. monocytogenes count of at least 5 log. Nine temperature time combinations, 75 °C, 85 °C and 90 °C applied for 15 min, 25 min and 40 min each were tested in ricotta wheels artificially contaminated with a mixture of 5 L. monocytogenes strains. Inactivation was assessed respectively one day and 30 days after heat treatment. The efficacy of treatments was evaluated based on the reduction in L. monocytogenes counts, on the impact on sensory properties and on the cost of the treatment. Two out of nine treatment combinations, i.e. 85 °C for 40 min and 90 °C for 40 min, were effective in reducing L. monocytogenes contamination level of 5 log. No significant difference was observed in sensory properties after the heat treatments. Therefore both combinations are eligible to conduct a successive study aimed to extend the shelf-life of ricotta salata up to several months.
•Post-lethality treatment on Listeria monocytogenes was assessed in ricotta salata.•A reduction of 5 log10 cfu g−1 in L. monocytogenes count was validated.•No effect of treatments on sensory properties was observed.
The BGO-OD experiment at the ELSA accelerator facility uses an energy tagged bremstrahlung photon beam to investigate the excitation structure of the nucleon. The setup consists of a highly segmented ...BGO calorimeter surrounding the target, with a particle tracking magnetic spectrometer at forward angles. BGO-OD is ideal for investigating low momentum transfer processes due to the acceptance and high momentum resolution at forward angles. In particular, this enables the investigation of strangeness photoproduction where t-channel exchange mechanisms play an important role. This also allows access to a kinematic region where extended, molecular structure may manifest in reaction mechanisms. The extensive strangeness photoproduction programme includes the photoproduction of neutral and charged kaons using both hydrogen and deuterium targets.
A
bstract
We present a measurement of
η
meson production in photon-photon interactions produced by electron-positron beams colliding with
GeV. The measurement is done with the KLOE detector at the
ϕ
...-factory DAΦNE with an integrated luminosity of 0.24 fb
−1
. The
e
+
e
−
→
e
+
e
−
η
cross section is measured without detecting the out-going electron and positron, selecting the decays
η
→
π
+
π
−
π
0
and
η
→
π
0
π
0
π
0
. The most relevant background is due to
e
+
e
−
→
ηγ
when the monochromatic photon escapes detection. The cross section for this process is measured as
σ
(
e
+
e
−
→
ηγ
) = (856 ± 8
stat
± 16
syst
) pb. The combined result for the
e
+
e
−
→
e
+
e
−
η
cross section is
σ
(
e
+
e
−
→
e
+
e
−
η
) = (32.72 ± 1.27
stat
± 0.70
syst
) pb. From this we derive the partial width Γ(
η
→
γγ
) = (520 ± 20
stat
± 13
syst
) eV. This is in agreement with the world average and is the most precise measurement to date.
A measurement of the vector to pseudoscalar conversion decay ϕ→π0e+e− with the KLOE experiment is presented. A sample of ∼9500 signal events was selected from a data set of 1.7 fb−1 of e+e− ...collisions at s∼mϕ collected at the DAΦNE e+e− collider. These events were used to perform the first measurement of the transition form factor |Fϕπ0(q2)| and a new measurement of the branching ratio of the decay: BR(ϕ→π0e+e−)=(1.35±0.05−0.10+0.05)×10−5. The result improves significantly on previous measurements and is in agreement with theoretical predictions.
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