Three-stepH−charge exchange injection with a narrow-band laser

Abstract

This paper presents a scheme for three-step laser-based stripping of an H ÿ beam for charge exchange injection into a high-intensity proton ring. First, H ÿ atoms are converted to H 0 by Lorentz stripping in a strong magnetic field, then neutral hydrogen atoms are excited from the ground state to upper levels by a laser, and the remaining electron, now more weakly bound, is stripped in a strong magnetic field. The energy spread of the beam particles gives rise to a Doppler broadened absorption linewidth, which makes for an inefficient population of the upper state by a narrow-band laser. We propose to overcome this limitation with a ''frequency sweeping'' arrangement, which populates the upper state with almost 100% efficiency. We present estimates of peak laser power and describe a method to reduce the power by tailoring the dispersion function at the laser-particle beam interaction point. We present a scheme for reducing the average power requirements by using an optical ring resonator. Finally, we discuss an experimental setup to demonstrate this approach in a proof-of-principle experiment.

First Demonstration of Laser-Assisted Charge Exchange for Microsecond Duration H− Beams

“…In 2006, this problem was overcome in a proof-of-principle (POP) experiment that utilized a diverging laser to induce a frequency sweep in the rest frame of the ion beam [6]. Consider the Doppler equation that relates the frequency of the laser in the lab frame to the frequency in the ion beam frame [7]:…”

Creating intense polarized electron beam via laser stripping and spin-orbit interaction

“…Therefore, we need more than order of magnitude reduction of the transition frequencies spread to get low power final stage laser and good separation of transition frequency to selectively excite states with needed polarization. To achieve this we employ the trick from [3], namely, we introduce the dispersion function in the stripping region such that the angles are correlated with energy and the derivative of the Doppler formula for laser light Lorentz transformation on energy is equal to zero. For this, the dispersion derivative D' must be:…”

“…Recently, high efficiently methods of laser-assisted electron stripping of hydrogen were developed (see, e.g. [2][3][4]) and experimentally demonstrated in Oak Ridge [5]. This was done with around 1 GeV SNS beam.…”

“…The initial acceleration to a few hundred keV has to be done either by low frequency RFQ or some other accelerator to match the 14 MHz frequency of the proton beam in RHIC. Then, the H -beam goes through the sequence of dipoles and quads creating a correlation of energy and angles and reducing its angular spread to minimize the absorption line width of the hydrogen states [3]. In addition, we have to reduce the ion bunch length in the dispersion section in order to make the electron beam, produced by the source, appropriate for further compression.…”

Effective calculation of laser stripping via a broad shape resonance

“…At present, the possibility of laser assisted charge exchange injection of a high-energy hydrogen beam with the help of powerful laser and magnetic fields is widely discussed [1][2][3][4][5][6][7]. A wide review on laser stripping and its achievements can be found in [2,3,7].…”