Cyclotron trap

Fig. 7. Lay-out of the 7tE5 area with Cyclotron Trap, magnetic channel MEK, PSC solenoid, and laser components...

The CCDs for the direct measurement of the antiprotonic X-rays were installed in the second bore hole of the cyclotron trap close to the stop volume. Thus, a few per mille of the full solid angle were covered. The relative efficiency and the in-beam resolution function were obtained in a separate measurement from the saturated X-ray transitions in pN. Two different types of CCDs were used (i) MOS CCDs with a typical depletion depth of about 30 pm [22,23] and (ii) the prototype of a high-rate X-ray detector based on a fully depleted (290 pm) pn-CCD [24],... 

Fig. 2. Set-up of cyclotron trap, crystal spectrometer, and CCD detectors in LEAR, experiment PS207. For the pH measurement, the two-arm crystal spectrometer was equipped in total with 3 spherically-bent quartz crystals each reflecting to a separate X-ray detector. Further CCD detectors installed in the second bore hole of the cyclotron trap were used for direct measurements of antiprotonic X-rays...

A different method became available with modern meson factories, where the characteristic X-radiation from exotic atoms can be studied under optimized conditions and with reasonable count rates. Such experiments require the use of high-intensity external beam lines together with a particle concentrator like the cyclotron trap and a high-resolution low-energy crystal spectrometer. 

Fig. 1. Principle of the set-up for the pion mass experiment consisting of the cyclotron trap with a gas cell and a curved-crystal spectrometer equipped with a two-dimensional position-sensitive X-ray detector. The focusing condition for a wave length A reflected under the Bragg angle Ob is R-sin B, where R is the (horizontal) radius of curvature. Typical values for R and the diameter of the spherically bent crystals are 3 m and 100 mm...

A possibility to extend this set comes from the use of an Electron-Cyclotron-Resonance-Ion-Trap (ECRIT), which will be realized using the cyclotron trap itself [22]. Here, hydrogen-like electronic atoms will be produced to obtain narrow calibration lines independent of an accelerator s pion beam. The radiative widths of light elements with Z k. 15 are of the order of a few 10 meV because of the absence of non-radiative inner-shell transitions. 

The shift and the width of the ground state in pionic hydrogen and deuterium have been determined in a series of experiments of the ETHZ-Neuchatel-PSI collaboration by measuring the 3-1 transition at 2886 eV with a reflection type crystal spectrometer [10]. An array of 6 cylindrically bent quartz crystals had been used in order to increase the statistics of the experiment. The pions were stopped in a cryogenic target inside a superconducting magnet (cyclotron trap I) and the X-rays were detected with CCD detectors developed at the University of Neuchatel. 

At the basis of the experiment are a newly designed cyclotron trap (cyclotron trap II), a single spherically bent crystal (silicon or quartz) and a new CCD... 

Fig. 3. The 2-1 transition in pionic deuterium measured with the Jiilich spectrometer and cyclotron trap II...

L. Simons, The cyclotron trap for antiprotons, Hyperfine Interact. 81 (1993) 253-262. 

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