Measured gas desorption and electron cloud effects with an intense ion beam in a solenoid lattice

Abstract

Electron cloud and gas measurements were conducted in a solenoid lattice with a 10 s, singly charged K ion bunch at an ion energy of 0.3 MeV and currents of 26 and 45 mA. The principal objective of these experiments is to control electrons and understand their impact on the beam dynamics. Electron clearing measurements indicate an electron density close to 1% of the beam density in the solenoid lattice is enough to partially neutralize the beam and cause the emittance to grow 40%. A new method of measuring the dynamics of beam-induced gas desorption, ionization, and electron emission for normal incidence is also presented. Stainless steel and copper targets exposed to a beam intensity of 1:6 10 12 ions=pulse show ionized gas and electron densities approach the beam density in a single pulse. These measurements also show the gas cloud expands as a function of time and the dynamics are dependent upon the incident material and the bias voltage.

Single-pulse and multipulse longitudinal phase space and temperature measurements of an intense ion beam

“…4) which reduced the transmitted beam current from 30 mA, which was incident on the slit plate, to $10 A for current densities $10-20 A=m 2 , eliminating space-charge effects in the spectrometer. Although this is a reduction in signal >3 orders of magnitude, it is similar to our transverse phase space measurements [13,14]. The beam ribbon traversed the 90 bend of the electrostatic dipole and was detected at the focal plane.…”

“…6. Recall the beam passes through a 0:1 mm wide  5 mm high slit plate and the measured transverse emittance is 14 m [14]. Beam expansion due to transverse emittance is small in the vertical direction and is confirmed by the height of the measured distribution in the top row of Fig.…”

“…This method is similar to that used for transverse phase space measurements [13,14]. The upstream slit is the same as described above (0:1 mm  5 mm) and the downstream slit was increased to 0:1 mm  10 mm to compensate for beam expansion due to the transverse emittance in the vertical (nonbend) plane.…”

“…This is a low . With this diagnostic we could monitor the image charges that were observed when the beam entered and exited the spectrometer and if any charge was collected on the plates due to scraping or beam loss [13,14]. Unless the voltage on the dipole was not set to steer the beam through there was negligible charge collected aside from the image currents.…”

“…This energy is slightly below the 1.9 MeV Bragg peak, which is the required energy to optimize uniform heating through electronic stopping power at the center of the $m-thick Al target heated by a Li þ ion driver [7][8][9][10]. The neutralized drift compression experiment (NDCX) at LBNL is exploring the physical limits of compression and focusing of ion beams and conducting preliminary WDM experiments [11][12][13][14][15]. In preparation for NDCX-II, the longitudinal phase space and temperature measurements described herein were used to quantitatively understand the requirements for the acceleration diode, acceleration schedule, and velocity tilt.…”