Rough schematic of the DESIREE facility.
Edge view cross section of DESIREE. The labels correspond to; A: I-beam support structure, B: cryocoolers and turbo pumps, C: pumping ports, D: thin-walled supports, E: motion feedthrough and measurement system, F: steel outer chamber, G: super insulation, H: copper screen, I: aluminium inner chamber, J: ion injection ports, K: Bellows, L: Copper braids, M: Optical windows, and N: Cold baffles.
Schematic of the DESIREE ion-optical structure. The ring on the top in this view is referred to as ring 1 (R1) while the other ring is ring 2 (R2). The dashed line represents the orbit of the ions. The steering, focussing, and correction elements are: CC&CV-Correction element, CD-160° deflector, DE-10° deflector, D1&D2-Deflectors, and QD-Quadrupole doublet. Detectors and measurement devices are: FC-Faraday cup, PU-Pick-up, ID-Imaging detector, MD-Movable neutral detector, SD-Stationary neutral detector, and MC-Movable charged fragment detector. RF-Radio frequency kicker. Finally, the straight sections and the merging region are SS and MR, respectively.
Results from the initial cryocooler tests. The temperature of the 1 and 2 stages was measured as a function of cooling power (lines) and compared to the manufactures data (symbols). The inset highlights the lowest temperature region.
A typical result illustrating the temperature of the inner aluminium chamber in the test chamber as a function of the cooling-down time. The inset gives an indication of the stabilisation time.
The design (left) and finished model (right) of a movable detector for use at cryogenic temperatures in DESIREE.
The storage lifetime of Ar+ and He+ ions as a function of the pressure in the vacuum chamber. The experimental data are shown by the solid symbols, and the solid line is a linear fit to the data points and shows good agreement with the expected relation of inverse proportionality between the storage lifetime and the pressure.
Example results for the calculated horizontal (solid line) and vertical (dashed line) size (“radius”) of a beam with a symmetric emittance ε = 10π mm mrad as a function of position around Ring 1. The hatched areas to the left and right indicate the straight and merging sections, respectively.
As Fig. 8 but for a beam with a symmetric emittance 3π mm mrad stored in Ring 2.
Technical 3D drawing showing the seven elements that make up the drift tube in the merging region.
A picture taken during mounting of the ion-optical elements in the inner chamber. The view is from just above the imaging detector in the direction of the merging region.
A block schematic showing the seven elements that make up the drift tube in the merging region of DESIREE together with the pick-up elements located on either side of this region. Three different examples of electrical-connection schemes are shown and these are explained in the text.
The centre-of-mass collision energy, E cm , between a 26 keV H+ beam and a 24 keV H− beam in the merged region as a function of the applied drift voltage, U T . The inset shows an expanded view around the minimum of the collision energy. The expected lowest accessible collision energy of 10 meV is indicated by the hatched area.
Product particle separations, in distance (solid and dashed lines) and in arrival times (dotted lines), in the mutual neutralisation reaction H− + H+ → H(1) + H(n), n = 1, 2, 3, 4. The arrow indicates the active diameter of the imaging detector. The hatched area is explained in the text. Plot (a) shows all particle separations while Plot (b) shows only particle separations for which the difference in the arrival time of the particles is less than 800 ps.
The calculated MN reaction count rate (solid line) as a function of the tuning voltage on the merging region. Also plotted is the data shown in Fig. 13 (dashed-line). The hatched area indicates where (in applied voltage) the MN counts come from collisions with E cm ⩽ 10 meV.
The primary sources of thermal input (radiative and resistive heating) into the copper screen and the inner chamber. The four cryocoolers connected to the copper screen with their first stages can sink a heat load of ≈200 W at 50 K while connected to the aluminium chamber by their second stages can sink ≈10 W at 5 K.
The companies involved in supplying components used in the construction of DESIREE.
Design parameters for R1 and R2 in DESIREE. All element lengths, separations and radii are given in mm with a tolerance in all dimensions of 0.1 mm. All nominal operating voltages are bipolar and are given in ±kV, and where tolerances are supply and DAC dependent
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