Lorenz Willmann

New bounds from a search for muonium to antimuonium conversion

A new upper limit for the probability of spontaneous muonium to antimuonium conversion was established at P-M (M over bar) less than or equal to 8.3 x 10(-11) (90% C.L.) in 0.1 T magnetic field, which implies consequences for speculative extensions to the standard model. Coupling parameters in R-parity-violating supersymmetry and the mass of a flavor diagonal bileptonic gauge boson can be significantly restricted. A Z(8) model with radiative mass generation through heavy lepton seed and the minimal version of 331 models are disfavored. [S0031-9007(98)08068-5].

A MEASUREMENT OF THE 1S-2S TRANSITION FREQUENCY IN MUONIUM

Doppler-free two-photon laser spectroscopy has been employed to measure the 12S12−22S12 transition in the muonium atom (μ+e−). A value of 2 455 529 002(33) (46) MHz has been obtained, which agrees with QED calculations within two standard deviations. The Lamb shift contributions are tested to the level 8×10−3. The corresponding measurements in hydrogen and deuterium using the same apparatus and laser system provide a test of the applied systematic corrections and have verified the systematic error of 46 MHz quoted. The mass of the positive muon has been derived from the isotope shift in this transition and yields a value of 105.65880(29)(43) MeVc2.

Dual magnetic separator for TRI mu P

The TRIμPTRIμP facility, under construction at KVI, requires the production and separation of short-lived and rare isotopes. Direct reactions, fragmentation and fusion–evaporation reactions in normal and inverse kinematics are foreseen to produce nuclides of interest with a variety of heavy-ion beams from the superconducting cyclotron AGOR. For this purpose, we have designed, constructed and commissioned a versatile magnetic separator that allows efficient injection into an ion catcher, i.e., gas-filled stopper/cooler or thermal ionizer, from which a low energy radioactive beam will be extracted. n nThe separator performance was tested with the production and clean separation of 21Na ions, where a beam purity of 99.5% could be achieved. For fusion–evaporation products, some of the features of its operation as a gas-filled recoil separator were tested.

Production of radioactive nuclides in inverse reaction kinematics

Efficient production of short-lived radioactive isotopes in inverse reaction kinematics is an important technique for various applications. It is particularly relevant when the isotope of interest is only a few nucleons away from a stable isotope. In this article production via charge exchange and stripping reactions in combination with a magnetic separator is explored. The relation between the separator transmission efficiency, the production yield, and the choice of beam energy is discussed. The results of some exploratory experiments will be presented.

Development of a thermal ionizer as ion catcher

An effective ion catcher is all important part of a radioactive beam Facility that is based on in-flight production. The catcher stops fast radioactive products and emits them as singly charged slow ions. Current ion catchers are based on stopping in He and H-2 gas. However, with increasing intensity of the secondary beam the amount of ion-electron pairs created eventually prevents the electromagnetic extraction of the radioactive ions front the gas cell. In contrast, such limitations are not present in thermal ionizers used with the ISOL production technique. Therefore, at least for alkaline and alkaline earth elements, a thermal ionizer should then be preferred. An important use of the TRI mu P facility will be for precision measurements using atom traps. Atom trapping is particularly possible for alkaline and alkaline earth isotopes. The facility call produce up to 10(9) s(-1) of various Na isotopes with the in-flight method. Therefore, we have built and tested a thermal ionizer. An overview of the operation, design, construction, and commissioning of the thermal ionizer for TRI mu P will be presented along with first results for Na-20 and Na-21. (c) 2008 Elsevier B.V. All rights reserved.

An efficient position sensitive detector for 3-30 keV positrons and electrons

Abstract A position sensitive detector for 3–30 keV positrons and electrons has been developed which consists of a pair of microchannel plates (MCP) in Chevron configuration and resistive anode readout. The device has an active diameter of 75 mm and can be operated in axial magnetic fields up to several kG. The detection efficiency of MCP devices is 16(2)% for positrons in the 10 keV region. With a thin carbon (C) foil of 25 μg/cm 2 thickness carrying a 15 μg/cm 2 magnesium oxide (MgO) coating acting as additional secondary electron emitter, the efficiency could be increased to 64(2)% in the energy range 5–12 keV. A two-dimensional position resolution of 0.55(3) mm (FWHM) and a timing resolution of better than 1 ns could be achieved.

Precision spectroscopy of trapped radioactive radium ions

Atomic parity violation (APV) can be measured in a single Ra+ ion, enabling a precise measurement of the electroweak mixing angle in the Standard Model of particle physics at low momentum transfer. This provides sensitivity to new particles such as extra Z0 bosons or leptoquarks. The Weinberg angle can be measured via a determination of the light shift in the forbidden 72S1/2–62D3/2 transition in a single trapped Ra+. Ultra-narrow transitions in such an ideal system can also be exploited to realize a high stability frequency standard. At the TRIμP facility of KVI, we have succeeded in the production of a series of radioactive short-lived radium isotopes. The radium isotopes produced were stopped and thermalized to Ra+ in a thermal ionizer, mass separated in a Wien filter, cooled in a gas filled radio frequency quadrupole and subsequently trapped as a cloud in a linear Paul trap. Laser spectroscopy in the trapped radium ions has been performed. The results of hyperfine structure, isotope shift, and lifetim...

The muonium atom as a probe of physics beyond the standard model

The observed interactions between particles are not fully explained in the successful theoretical description of the standard model to date. Due to the close confinement of the bound state muonium (

Spectroscopy of the 1S-2S energy splitting in muonium

M = mu^+ e^-

Dual magnetic separator for TRIμPTRIμP

) can be used as an ideal probe of quantum electrodynamics and weak interaction and also for a search for additional interactions between leptons. Of special interest is the lepton number violating process of sponteanous conversion of muonium to antimuonium.