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1

Computer simulation of the space charge dominated beam dynamics for external injection into the JINR Phasotron

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Onischenko L. , Samsonov E.

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tom Vol. 48,suppl.2

29-34

EN

A project of increasing the beam intensity of the 660 MeV JINR proton Phasotron up to 50 žA by an external injection of the H- beam with energy of 5 MeV is now under design. Computer simulation of the space charge dominated beam dynamics in Phasotron is reported. As follows from the simulation, the capture efficiency does not change too much when the beam space charge is taken into account.

2

Space charge dominated beam transport in the K130 cyclotron injection line

100%

Heikkinen P.

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tom Vol. 48,suppl.2

21-24

EN

High intensity H- beams are injected into the K130 cyclotron [1] for isotope production and for proton induced fission studies. Earlier, when protons were accelerated as positive ions, the beam intensity was limited by beam losses in the extraction system from the cyclotron. Stripping extraction of negative ions removed this limitation. However, now space charge effects in the injection beam line limit the beam intensity. At present, the maximum practical H- beam intensity at the inflector is about 0.25 mA, which gives 40-50 žA of extracted proton beam. Calculations predict that the injection beam line from the ion source to the matching quadrupoles below the cyclotron can transfer about 1 mA of 6 keV H- beam, which also was measured. The quadrupole section has a smaller transmission. Also a significant portion of the beam is lost during the last 2 m in the axial hole. General rules for maximum beam intensity as a function of beam line parameters such as beam tube aperture, distance of focusing elements, beam charge, mass and energy are given for different kinds of focusing systems (solenoids, FODO and FOFDOD quadrupole structures). As a conclusion, some suggestions to improve the transmission of the injection line are given.

3

Measurements of frozen-in polarization in PET electrets using E-j method

100%

Motyl E.

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tom Vol. 40, nr 15

41-45

EN

Step elcctroacoustic (SEA) and thermally stimulated depolarisation (TSD) techniques were applied for analysis of electret slate in polyethylene-terephthalate samples after corona charging at low and high temperatures. Measurements of electric field distributions E and current density jTSD during thermally stimulated discharging allow to get information on real charge density and quasi-frozen polarisation in dielectric. The above E-j method is a useful tool for measurement of local values of real and polarization charges in PET electrets and their decay in time. Positive and negative coronas as well as temperature of charging affect the storage of real charges and polarisation in PET electrets.

4

Local space charge effect in conventional avalanche counters at moderate specific ionization

88%

Sernicki J.

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tom Vol. 45, nr 2

125-131

EN

The purpose of this investigation is the determination of a simple criterion of local space charge effect in conventional avalanche counters at moderate specific ionization. Parallel-plate avalanche counters (PPAC) with an electrode spacing d from 0.1 to 0.4 cm have been used to register low-energy alpha particles at n-heptane vapour pressures of p ? 5 Torr. The criterion determined is a simple h/pm function describing the variability of the product of effective gas amplification and actual particle energy loss, where both the numerical h coefficient and the exponent m assume different values for the various values of d. The product variability at higher gas pressures in PPAC detector – having regard to practical side of criterion determined – can be relatively well described by a single linear function. The results obtained are discussed from their veracity point of view.

5

Partial discharge analyses ‒ a comparison of different parameters used

88%

Benzerouk D. , Patsch R. , Menzel J.

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tom Vol. 40, nr 15

46-50

EN

In the past many approaches have been made to use partial discharge signals to monitor and characterize degradation processes in electric equipment. For the on-line monitoring of large machines or transformers or periodic off-line inspections in many cases only the change of the phase angle distributions of the occurrence of discharges is taken as an indicator for ageing processes in the insulating system. This is sufficient as an indication for the need of a more detailed examination, but often even with off-line experiments the actual change in the defect and especially its relevance for the service life remains unclear. A more detailed insight into the physics of the local degradation processes and their relevance for the ageing process of the equipment can be gained in most cases only with measurements with a continuously increased voltage load and the evaluation of the data via Pulse Sequence Analysis. The paper will discuss and compare different methods to analyze partial discharge data, starting with 'simple' frequency distributions of different parameters of the externally applied voltage load derived from the data set as a whole. As the main point sequence correlated data such as time differences between consecutive discharges will be discussed. It will be shown that in dependence on the type of defect the significance of different parameters is different.

6

The Effect of Protrusions on the Initiation of Partial Discharges in XLPE High Voltage Cables

63%

AlShaikh Saleh M. , Refaat S. S. , Olesz M. , Abu-Rub H. , Guziński J. , AlShaikh Saleh M. , Refaat S. S. , Olesz M. , Abu-Rub H. , Guziński J.

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