2361080
Space-charge-dominated bunched beams in the frequency domain.
14940456
Incoherent effect of space charge and electron cloud
Trapping by resonances or scattering off resonances induced by space charge (SC) or electron cloud (EC) in conjunction with synchrotron motion can explain observations of slow beam loss and emittance growth, which are often accompanied by changes in the longitudinal beam profile. In this paper we review the recent progress in understanding and modeling of the underlying mechanisms, highlight the differences and similarities between space charge and electron cloud, and discuss simulation results in the light of experimental observations, e.g., at GSI, CERN, and BNL. In particular, we address the role of the pinched electrons and describe in detail the complexity of the electron pinch formation. We present simulation results within a dipole or in a field-free region of the beam pipe, which reveal the morphology and main features of this phenomenon, explain the physical origin of the complex electron structures like stripe in either field configuration, and discuss the dependence on some key parameters.
33181516
Status Report of the Experimental and Theoretical Investigations in the Garching Electron Ring Accelerator
In the Pustarex electron ring accelerator low-intensity electron rings were accelerated without ions. Rings with larger electron numbers ran into instabilities with a radial precessional mode, which led to ring widening and particle losses. With resistive walls this instability - probably the resistive wall instability - occurred rather early. After replacement of the resistive walls by capacitive walls the instability happened mostly at the end of compression. Rearrangement of the system is planned to improve the symmetry of the fields and enhance the Landau damping coefficient. To increase the negative mass threshold of the number of trapped electrons in the ring, a beam with instantaneous energy spread has been developed. An arrangement which results in a beam with two energy peaks 5% apart is described. Also connected with the negative mass instability are calculations of the coupling impedance of an electron ring to a realistic squirrel cage. A few of the results, which show a rather large impedance with additional resonances, are presented. The present paper reports three main subjects: 1. the experiments with the Garching Pustarex electron ring accelerator; 2. results of an experiment to produce electron beams with instantaneous energy spread; 3. calculations of the coupling impedance of an electron ring to a squirrel cage structure.
54651064
Scaling laws for crossing of space charge resonances
Crossing of intrinsic space charge resonances may lead to emittance variations depending on the strength of space charge, the crossing rate and the lattice. We present scaling laws for the the “Montague-” coupling resonance near 2Qx − 2Qy =0 , and for the fourth order structure resonance near 4Qy =1 2, which are expressed in terms of simple algebraic expressions and benchmarked on fully selfconsistent particle-in-cell simulations in the 2D coasting beam limit.
118229317
Space charge dominated beams
120082181
Suppression of microwave instabilities
22334083
Proton spectroscopy beyond the drip line near A=150.
The Daresbury recoil separator has been used to measure proton radioactivity from the nuclei [sup 150]Lu, [sup 151]Lu, and [sup 147]Tm, produced using the reactions [sup 58]Ni+[sup 96]Ru[r arrow][sup 154]Hf[sup *] and [sup 58]Ni+[sup 92]Mo[r arrow][sup 150]Yb[sup *]. The half-life of [sup 150]Lu has been measured for the first time as 35[plus minus]10 ms, which identifies the proton decay as an [ital l]=5 transition from the [ital h][sub 11/2] proton state. New half-life and energy measurements have been made for the known proton transitions from [sup 147]Tm and [sup 151]Lu, which have been unambiguously assigned using the direct mass identification of the recoil separator. A new half-life measurement of the proton emitter [sup 109]I is also reported.