Abstracts Brochure - CERN

THPCH139
THPCH140
THPCH141
29-Jun-06 16:00 - 18:00 THPCH — Poster Session
Development of an Ion Source via Laser Ablation Plasma
F. Belloni, D. Doria, A. Lorusso, V. Nassisi (INFN-Lecce) L. Torrisi
(INFN/LNS)
428
Experimental results on the development of
a laser ion source (LIS) are reported. LISs
are particularly useful in ion accelerators, ion
implanters and devices for electromagnetic
isotope separation. A focused UV laser beam (0.1 - 1 GW/cm 2 power density) was used to produce a plasma plume
from a Cu target. Several aspects were investigated: ion angular distribution, energy distribution, ion extraction and
charge loss due to ion recombination. Particular attention was devoted to avoid arcs during the extraction phase; it was
accomplished by allowing the proper plasma expansion in a suitable chamber before the extraction gap. Diagnostics
on free expanding plasma and extracted ions was carried out mainly by time-of-flight measurements, performed by
means of Faraday cups and electrostatic spectrometers. At 18kV acceleration voltage, the ion beam current, measured
along a drift tube at 147cm from the target, resulted modulated on ion mass-to-charge ratio and its maximum value
was 220uA. The Cu+1 ion bunch charge was estimated to be 4.2nC. Ion implantation tests were successfully performed
at high acceleration voltage (several tens kV), by using a simple experimental arrangement.
New Pulsed Current and Voltage Circuits Based on Transmission Lines
We present two novel circuits able to com-
F. Belloni, D. Doria, A. Lorusso, V. Nassisi (INFN-Lecce)
press current or voltage pulse named current
compressor circuit (CCC) and voltage compressor
circuit (VCC), and two novel amplifier circuits able to double the current or voltage pulse. The compressing
circuits were composed by a transmission line, l long and a storage line, l/2 long. The CCC compressed the current
pulse by a factor of 2 doubling its intensity, while the VCC compressed the voltage pulse by a factor of 2 doubling its
amplitude. The amplifying circuits were composed by a R0 transmission line closed on a set of two parallel or series
storage lines which doubled the intensity of the pulses. The current pulse amplifier (CPA) had two R0/2 storage lines
in parallel, while the voltage pulse amplifier (VPA) had two 2R0 storage lines in series. The storage line was half long
with respect to the input-pulse. In both circuits, one storage line was characterized by an open extremity and the
other line by a closed extremity. Connecting the storage lines to suitable load resistors, R0/4, and 4R0 for the CPA and
VPA, respectively, a twice of the pulse intensity was obtained. The circuits were studied by computer simulations.
Control and Measurement of Wave Front of Femtosecond Single Electron Bunch
A. Yoshida, T. Kondoh, J. Yang, Y. Yoshida (ISIR) A. Ogata (HU/
AdSM)
Pulse radiolysis requires continuous
progress of time resolution to investigate
ultra-short chemical reactions. A 98 femtosecond
electron bunch has been produced
with a laser photocathode RF gun S-band linac and a magnetic bunch compressor. "Equivalent Velocity Method"
has been developed to get the high time resolution of pulse radiolysis by using femtosecond bunch. In the method,
wave front of the bunch should be rotated along the longitudinal direction to overlap with the wave front of the
analyzing light pulse. The wave front of the electron beam can be controlled by adjusting the RF phase in the linac
and optimizing the magnetic field in the compressor in order to rotate the bunch in the longitudinal phase space.
The rotation angle of the wave front of electron bunch in the horizontal and longitudinal plane was obtained by the
measurement of radiation light from the electron bunch with a femtosecond streak ca