Two examples of in-flight spin flippers
- PDF / 250,289 Bytes
- 4 Pages / 612 x 792 pts (letter) Page_size
- 47 Downloads / 177 Views
wo Examples of InFlight Spin Flippers1 I. A. Koop, A. V. Otboyev, P. Yu. Shatunov, and Yu. M. Shatunov Institut of Nuclear Physics SB RAN, Novosibirsk, 630090 Russia Abstract—In precise experiments with polarized beam it’s very often appear a necessity to change beam polarization on opposite. If such operation does not change other beam parameters, it helps to avoid or min imize some systematic errors. It is especially important in experiments, where spin dependent effect is small enough. This paper describes two set of equipments, that make spin flip for extracted beams. In both cases, these devices are absolutely distinct, because they are appropriate for different particles and at different energy range. The first of them is intended for future muon (g2) experiment, which is under preparation now at JPARC. Here, the muon spin flip will be done by chain of electrostatic and magnetic bends at the kinetic energy 340 keV. A beam matching is provided by a number of short solenoids. The other flipper (or Siberian snake) will rotate spin of protons or antiprotons, which come from Λmeson decay with the energy up to 40 GeV. This experiment (no. 24) is planed at IHEP, Protvino. In this case, two superconducting helical mag nets with opposite helicities and magnetic field 4.5 T will be used. To correct beam trajectory, additional dipole correctors are required. DOI: 10.1134/S106377961401050X 1
SPIN MANIPULATION AT JPARC
The muon (g2) experiment at JPARC is based on a usage of cold muons from muonium atoms ioniza tion [1]. The measurement of the spin precession fre quency will be done in a magnetic trap at the energy 350 MeV. Initial cold muons will be accelerated by a chain of linear accelerators. A first of them is RFQ linac accelerates muons up to kinetic energy 340 KeV (β ≈ 0.08). This energy is suitable for muon’s spin manipulations. We propose to install at this point some structure to work with polarization only, keeping other beam parameters unchanged. Let’s remind the main equations. Spin precession is described by the wellknown BMTequation: q q 0 + q' – Ω = ⎛ 0 + q'⎞ B ⊥ + B 䊐 ⎝γ ⎠ γ
In our case of very cold muon beam moving in electro static field, we obtain the spin tune: 2
– 1 + aμ ( γ – 1 ) ω ≅ –1. ν = = γ ω0
(1.3)
It means, that an electrostatic field for (γ2 – 1) Ⰶ 1 can bend a particle and does not rotates its spins. On other hand, it’s seen from (1.2), that a magnetic field rotates muon’s spin practically together with particle, due to a smallness of its magnetic anomaly. Hence, a simplest scheme for spin manipulation consists of two electrostatic bends and the Siberian snake between, which consists from two solenoids. Siberian snake rotates spin by 180 degree (Fig. 1). When spin manip
(1.1)
q0 + ⎛ + q'⎞ [ E × V ]. ⎝γ + 1 ⎠
Siberian snake
Introducing particle revolution frequency
+
–
+
+
q0 γq 0 [ E × V ], – ω 0 = B ⊥ + 2 γ γ –1
– r
we can rewrite (1.1) in the form:
L
1 ⎞ Ω – ω 0 = ω = q'B + q 0 ⎛
Data Loading...
