de Saint Simon, M

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Qi0lQ.}*Bratislava, P. Van Duppen, G. Correia, M. Lindroos, CERN, private communication. OCR Output1 H. Schiebler and D. Habs, MPI Heidelberg, M. de Saint Simon, CSNSM Orsay, K. Janko,estimated (probably over-estimated) from the source parameters to 5 x 10** (30 eV at 60 keV).than the former one probably because of the smaller aperture. The variance of the energy spread is38 rr mm mrad for 95 % of intensity, corresponding to 22 rr mm mrad at 60 keV, appears to be smaller(G. Alton, private communication) and the same data analysis procedure, the measured emittance isproduced a xenon beam extracted at 20 keV. Using the same kind of emittance—meter in Oak RidgeA plasma ion source of the ISOLDE type, with an aperture of 1.5 mm in diameter, has been used to:> Plasma ionization source60 ke\/).spread is estimated (probably over-estimated) from the source parameters, to be 2 x 10*4 (12 eV atintensity and 7.9 7C mm mrad (/MeV for 95% (32 vt mm mrad at 60 ke\/). The variance of the energy6.9 1: mm mrad t/MeV (un-normalized emittance e = 28 rz mm mrad at 60 keV) to keep 90 % of thebeam intensity contained in this emittance (figure 1). The normalized emittance is found to be SnThe analysis of the data allows to plot the relationship between the emittance and the fraction of thedegrees from the horizontal plane. The source setting-up and optimization were performed as usual.A wire current detector. The beam scanning is performed in 2 perpendicular planes shifted by 45line of ISOLDE. lt allows for direct emittance measurements with a moving slit upstream of a multiusing a specific device lent by D. Habs (MPI - Heidelberg) and installed at the end of the GHM beamThe 60 keV beam of 205TI+ produced in a tungsten tube, 3 mm in diameter, has been measuredl:> Surface ionization source1. ISOLDE beam emittance measurementsacceptance.to the beam characteristics : emittance and kinetic energy spread, and to the spectrometerat the resonance frequency to the incoming ISOLDE beam current. The transmission factor is linkedoverall transmission is de¤ned as the ratio of the beam current at the exit of the spectrometer tunedof accurate mass measurements of far from [3-stability nuclei which are produced with low yields. TheIn addition to the mass resolving power, the transmission is a crucial factor to determine the feasibilityemittance of the ISOLDE beam.transmission and of the lowest yield acceptable for mass measurement, resulting from the measuredaddendum will concentrate on the first question and will give an evaluation of the spectrometerHRS is not required. A 5 seconds duration for the voltage stepping is satisfactory. Therefore, this new: the GPS is better suited to feed the RF mass-spectrometer than the HRS and, consequently, thestepping will be". An answer to the last two questions was given in Addendum n°1 (CERN/ISC 93-36)b) whether the high resolution separator will be required or not and c) what the optimal voltage"a) whether low enough separator emittance can be achieved without sacrificing yield and timing, andof the 9'“ ISOLDE Committee (August 23-24, 1993) :After the presentation of the proposal P54, three technical questions were mentioned in the minutesSpokesman : M. de Saint SimonMass measurement of very short half-lived nucleipresented to the ISOLDE Experiment CommitteeO .3,, ,5% Addendum n 2 to the proposal P54GER M - IEC,sc>i>November 10, 199459 SC000002‘2', · *0 \lllllllllllllllllllllllllllllllY-R fvt CERN LIBRARIES. GENEVAmass measurement spreading further from stability. OCR OutputISOLDE facility, we know that the yields are even higher, allowing for a wider program of accuratebe carried out over more than 100 nuclei with half-lives shorter than 1 second. With the PS-Boostersuch a sensitivity limit and the known yields of the SC-ISOLDE facility, a wide physics program couldcorresponds to a yield lower limit of 10 atoms/s. The proposal has shown that, taking into accountDue to the background noise of the detector, close to 0.1 count per second, such a 1% transmission5. Conclusionenergy spread.are compatible with an average transmission of 1 %, particularly considering the over·estimate of theaccount the uncertainties on emittance measurements and energy spread estimation, those numbersThe observed dispersion of the results is a consequence of evaluation procedures. Taking intoPlasma 30.0 19.1 35.8 30.7 0.90Plasma 30.0 83.0 31.0 1 .3so l 22 l sooPlasma 30.0 26.7 46.1 57.3 2.4Plasma 44.0 71.0 58.0 4.0so l 22 l 30.0Surface 12.0 14.2 27.5 68.0 0.91Surface 8.5 30.0 68.0 0.38so I 45 l 12.012.0Surface 19.1 35.8 95.6 2.0Surface 60 I 32 I 12.0 12.0 41.0 99.0 1 .1keV I ni mm mrad I eV % I %@7 | 62Source I method | E | e95% | sigmaE | Q"}!down to 30 kV (forA = 250). The transmission is evaluated, in addition, for that borderline event.magnetic field, the ISOLDE high voltage has to be progressively decreased from 60 kV (for A = 100)cuts due to horizontal, vertical and energy cuts. Because of a limitation of the intensity of thethe beam kinetic energy, sigma E the variance of the energy spread, 5]%, QQ) and 5<E are partialand 52 are the overall transmissions obtained with the first and the second method respectively. E isThe transmission is evaluated forthe two types of ion source. The results appear in Table 1 where 514. Results of the transmission evaluationrealistic than the previous one.is no need to evaluate the spectrometer acceptance. Therefore, this method is certainly moreenergy dispersion. Here, correlations between the cuts are implicitly taken into account, and therespectrometer. The particle generation assumes gaussian distributions in location, angles and• ln the second method, the transmission is evaluated using a multi-particle simulation of the wholeaberrations at each slit (90 %).energy spread. An additional cut has been introduced to take into account the cut due to opticalthe beam (figure 1). The energy cut has been calculated assuming a gaussian distribution of theevaluated from the relationship between the measured emittance and the transmitted fraction of ·.• The various cuts are supposed to be independent from each other. The geometrical cuts areThe transmission evaluation has been performed using two methods :Methods used for the transmission evaluationamplitude cut.Phase (time) acceptance : 1/3. This value corresponds to the regular setting leading to a halfKinetic energy spread acceptance : ·; = i 4 *104 (48 V at 60 keAEav = 8 1: mm mradVertical plane : 1 5.0 mm, 1 1.6 mrad vertical acceptance :Horizontal plane : 1 0.2 mm, 110 mrad horizontal acceptance : aH = 2 n mm mradacceptance is as following :these cuts are due to four 0.4 x 10 mm? slits located along the trajectory. The spectrometerangle, kinetic energy cut and phase (time) cut due to the phase dehning slit. Except for the last one,The spectrometer makes three different cuts in the beam current 1 geometrical cuts in position and2. RF mass-spectrometer acceptanceBeam : Z°*’T|", W-surface ionizer, intemal diameter : 3 mm (from ‘).Figure 1. Normalized emittance versus percent of beam current for the surface ionization source.Current/Total current604020 80 100X-emittance (U11)g 1012

Mass measurement of very short half-lived nuclei

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