Ion beam development for the needs of the JYFL nuclear physics programme.

The increased requirements towards the use of higher ion beam intensities motivated us to initiate the project to improve the overall transmission of the K130 cyclotron facility. With the facility the transport efficiency decreases rapidly as a function of total beam intensity extracted from the JYFL ECR ion sources. According to statistics, the total transmission efficiency is of the order of 10% for low beam intensities (I(total)< or =0.7 mA) and only about 2% for high beam intensities (I(total)>1.5 mA). Requirements towards the use of new metal ion beams for the nuclear physics experiments have also increased. The miniature oven used for the production of metal ion beams at the JYFL is not able to reach the temperature needed for the requested metal ion beams. In order to fulfill these requirements intensive development work has been performed. An inductively and a resistively heated oven has successfully been developed and both are capable of reaching temperatures of about 2000 degrees C. In addition, sputtering technique has been tested. GEANT4 simulations have been started in order to better understand the processes involved with the bremsstrahlung, which gives an extra heat load to cryostat in the case of superconducting ECR ion source. Parallel with this work, a new advanced ECR heating simulation program has been developed. In this article we present the latest results of the above-mentioned projects.

Experimental evidences for emittance degradation by space charge effect when using a focusing solenoid below an electron cyclotron resonance ion source.

Solenoids are widely used to provide initial focusing of beams extracted from an ion source. However, in the case of an electron cyclotron resonance (ECR) ion source, the extracted beam will usually include different ion species and for each of them a wide distribution of charge states. When such a multicomponent beam is focused by a solenoid, the ions with a Q/A larger than the beam of interest are overfocused and usually go through a waist before reaching the analyzing magnet. If the beam currents obtained for these ions are sufficient, the resulting space charge forces can significantly degrade the emittance of the beam components with a lower Q/A and result for those in a hollow beam. Using a beam viewer and an emittance-measuring device, this paper reports on experimental findings that confirm the existence of such an effect for low charge states of argon. Moreover, by changing the experimental conditions of the ECR plasma in order to modify the charge state distribution of the extracted ion beam, it is shown that the threshold where this space charge effect starts to be significant can be changed.

Prospects of ion beam extraction and transport simulations.

Beam profile measurements using viewing targets and emittance measurements with pepper pot devices have established new insights about the ion beam extracted from an electron cyclotron resonance ion source (ECRIS). In our measurements we have compared two different ECRISs of CAPRICE type, one source was equipped with a standard 1.0 T hexapole magnet, whereas for the other ion source a stronger hexapole magnet with a flux density of 1.2 T has been installed. The resulting ion beam profile for each individual charge state produced by different focal strengths of an optical element can be used to estimate the emittance, but it also shows the negative influence of the hexapole on the extracted ion beam. A hexapole correction would be desirable to improve further beam transport. A possible correction scheme will be discussed. All experimental observations can be reproduced by computer simulation if a magnetic plasma is assumed. When the Larmor radius for ions becomes small, collisions are negligible for the path of ions within the plasma. Low energy electrons are highly movable along the magnetic field lines and can compensate the ion space charge within the plasma chamber.

Avoidance of vascular complications associated with the use of dopamine.

Dopamine, dihydroxyphenylethylamine has three distinct actions depending on dosage. Low doses in the range of 1-2 mcg/kg/min result in vasodilatation. Medium doses of 2-10 mcg/kg/min increase cardiac output due to beta adrenergic action, while above 10 mcg/kg/min a potent vasoconstrictor effect predominates. Because of this last action great care must be used to avoid extravasation of infusions of dopamine directly into the tissue. Dopamine is a very useful agent but carries great potential to do local damage. Administration through a catheter placed into a large vein is recommended. Should extravasation occur, prompt infiltration of the area with phentolamine and a local anaesthetic, local cooling and regional sympathetic block may reduce the damage. The case is reported of a patient who suffered extensive necrosis in the forearm following local extravasation of dopamine.