Nuclear Instruments and Methods in Physics Research B 294 (2013) 397–402

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Nuclear Instruments and Methods in Physics Research B

journal homepage: www.elsevier .com/locate /n imb

The physics behind the isobar separation of 36Cl and 10Be at the French AMSnational facility ASTER

Emmanuelle Nottoli a, Maurice Arnold a,b,⇑, Georges Aumaître a,b, Didier L. Bourlès a,b,Karim Keddadouche a,b, Martin Suter a,c

a CEREGE, CNRS-IRD-Aix-Marseille Université, F-13545 Aix-en-Provence, Franceb ASTER-Team, CNRS-IRD-Aix-Marseille Université, F-13545 Aix-en-Provence, Francec Ion beam physics, ETH Zurich, Schafmattstr. 20, 8093 Zurich, Switzerland

a r t i c l e i n f o a b s t r a c t

Article history:Received 1 June 2011Received in revised form 12 January 2012Available online 18 February 2012

Keywords:Charge state distributionStopping powerEnergy stragglingIsobar separationAccelerator mass spectrometry

0168-583X/$ - see front matter � 2012 Elsevier B.V.doi:10.1016/j.nimb.2012.01.052

⇑ Corresponding author at: CEREGE, CNRS-IRD-Aix-Aix-en-Provence, France.

E-mail address: arnold@cerege.fr (M. Arnold).

The French AMS national facility ASTER, based on a 5 MV Tandetron accelerator, uses a degrader foilinstalled behind the focal plane of the 90�-high energy magnet for 10Be and 36Cl analyses. Ions passingthe 1000 nm silicon nitride degrader foil are analyzed with a 35�-Electrostatic Analyser (ESA) and a30�-magnet (vertical plane). The horizontal beam profiles were measured. For 30 MeV Cl ions, weobserved a very narrow beam width, which is well described by a normal distribution. Correspondingscans of 9Be and 10B at 11.2 MeV, however, revealed much wider beam widths and showed tails on bothsides that could not be described by a normal distribution. These non-normal distributions can be inter-preted to result from the coulomb-explosion that occurs during dissociation of the BeO� or BO� mole-cules in the terminal. In an additional experiment, the energy loss in the silicon nitride foil and theassociated energy straggling were measured and compared with models. Finally, charge state distribu-tions were determined for 36Cl exiting the degrader foil at 23.9 and 19.8 MeV. These distributions are welldescribed by Gaussian functions and the associated positions and widths agree quite well with publishedvalues for carbon foils.

� 2012 Elsevier B.V. All rights reserved.

1. Introduction

One of the limitations in AMS is isobaric background. Variousmethods are applied for the isobar separation. Most common areDE–E gas ionization detectors. However, if count rates are higherthan a several thousand particles per second, additional techniquesare needed. For 10Be analysis of typical environmental samples, aboron rejection of 108–1010 is needed. At energies above about10 MeV, an absorber technique can be successfully applied. The10B is stopped in an absorber (foil or/and gas) having the appropri-ate thickness and the 10Be is transmitted. It can then be detectedand identified in a gas detector [1]. At lower energies, the absorbermethods produce straggling ranges too large to allow a proper sep-aration. In addition, 9BeH molecules can survive the stripping pro-cess when selecting charge state 1+ or 2+. The resulting 9Befragments are then not stopped in the absorber. Therefore this ab-sorber technique is not appropriate at low energies. Another foiltechnique (called in this paper degrader foil technique) can be usedat lower energies. Using this method, the isobar 10B is not

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Marseille Université, F-13545

completely stopped in the absorber but since it loses a largeramount of energy than 10Be, the two can be separated with anadditional magnetic or electrostatic analyzer. This concept wasintroduced by Raisbeck et al. [2] to perform 10Be analyses at around5 MeV. Since then this method has also been used at much lowerenergy for 10Be measurements (0.75 MeV) as shown at ETH [3].In this case a significant improvement was attained by using muchmore homogeneous silicon nitride foils and a new generation ofgas detectors [4,5]. This degrader foil technique was also appliedfor separating other isobaric pairs such as S from Si [6]. The com-pany HVEE proposed applying this method also for the 36S–36Clseparation [7,8].

The first AMS system equipped for 36Cl–36S as well as for10Be–10B separation with this degrader foil technique is the French5 MV national facility ASTER manufactured by HVEE. This set-upand its performance have been described in various publications[9,10]. The goal of this work was to systematically study the degra-der foil method at ASTER in order to: (i) understand performanceand limitations of this method; (ii) propose possible improve-ments; (iii) compare the obtained data with models to determineto what extend models and semi-empirical formulas can be reli-ably used for optimizing the technique and predicting the perfor-mance of specific designs.

398 E. Nottoli et al. / Nuclear Instruments and Methods in Physics Research B 294 (2013) 397–402

2. Instrumentation and operating conditions

The French AMS national facility ASTER, based on a 5 MV Tande-tron accelerator, uses a degrader foil installed behind the focalplane of the 90�-high energy magnet for the 10Be and 36Cl analyses.Ions passing the silicon nitride foil, which has a nominal thicknessof 1000 nm and a round aperture of 5 mm radius, are analyzedwith a 35�-ESA (r = 2.6 m, horizontal plane) and a 30�-magnet(r = 1.5 m, vertical plane). Two quadrupole-doublet lenses are usedfor beam focussing. The limitation in angular acceptance is givenby the ESA plates (4 cm gap) and the apertures in front of the sec-ond quadrupole-doublet lens. The AMS-system provides conve-nient beam diagnostic tools. The software allows scanning all ofthe optical element power supplies while simultaneously measur-ing beam intensities with faraday cups or detectors. Variable slitsallow the resolution to be chosen at both the foil and detector loca-tions. All the measurements presented here were done without anymodification of the equipment or software. More details on the set-up can be found in [9,10].

3. Beam profiles

Isobar separation with the degrader foil method depends on thebeam size and shape at the foil location. This beam size is related tothe characteristics of the beam extracted from the source and to itssubsequent transport though the accelerator up to the location ofthe foil. In addition, the stripping process in the terminal as wellas high voltage fluctuations can result in a spreading of the beamin the focal plane of the high energy magnet and an enlargementof the beam in the horizontal plane. Because it is not trivial toproperly estimate all these effects, it was decided to experimen-tally measure the horizontal beam profile at the foil location. Thisprofile was obtained by measuring, through narrow slits (openingtypically 0.5 mm), the beam current in a Faraday cup at the foillocation as a function of the terminal voltage scanned in smallsteps. A position scale is derived using the dispersion of the highenergy magnet as given by the manufacturer (k = 3740 mm, forDx = DE/E⁄k). This dispersion was confirmed experimentally (with-in 2%) by moving the narrow slits in front of the Faraday cup by2 mm and comparing the terminal voltages for both scans. The pro-file might have some small distortions due to the band width lim-itations of the current amplifiers or due to delays in the terminalvoltage settings. This might cause some small asymmetry in theprofiles, but the induced effects are not relevant for the followingdiscussion. In Fig. 1 the results are shown for 37Cl (30 MeV, 5+),9Be and 10B (11.2 MeV, 2+).

For 37Cl, very narrow beams well described by normal distribu-tions (standard deviation: r ffi 0.6–0.7 mm) are observed (Fig. 1a).These results demonstrate the good ion optics with low aberration,

-10 -5 0 5 10Position (mm)

0

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30

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37ClExperimentGaussian fit

(a)

-10 -5 0Posit

0

2

4

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8

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rent

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)

9BeExperimentGaussian fit

(b)

Fig. 1. Measured beam profiles for (a) 37Cl (30 MeV), (b) 9Be and (c) 10B (11.2 MeV) with37Cl (a), narrow beams (r ffi 0.6–07 mm), which can be well described by normal distri2 mm) profiles are evidenced. Only their central part can be represented by normal distribdissociation of the BeO and BO molecules into charged fragments (Coulomb explosion).

and the excellent voltage stability of the terminal. The narrowbeam widths found with Cl have only a minor effect on the sepa-rating power of the degrader foil method.

For 9Be and 10B, (Fig. 1b and c), profiles are significantly wider(r ffi 1.7–2 mm). Only their central part can be modeled by normaldistributions, tails occurring on both energy sides. This larger beamsize and the tails can neither be explained by energy straggling norby ion optical effects. Similar enlargements and tails have beenfound in the energy profiles from the dissociation of NC�moleculesstripped at 1 MV [11]. The authors of this paper assigned thisbehavior to the coulomb explosion in the molecular break-upand made estimates of this effect. Based on their results and inter-pretation, we also studied the Coulomb explosion models for theinterpretation of our data. The effect of the dissociation of fastmoving molecules in foils has been studied for many systemsand is called ‘‘Coulomb Explosion’’. In solids, the molecular frag-ments are stripped to positive charge states within very short dis-tance and time and therefore the Coulomb repulsion of thefragments can be quite large. This process leads to significant deg-radation of the beam quality. Measuring the pattern (velocity andangle) of the molecular fragments can yield information on themolecular structure of the ion [12,13]. In the AMS literature, it ismentioned that foil stripping of BeO may cause significant beamlosses and that a combination of gas and foil stripping might bethe best solution to get a high stripping yield [1]. For gas strippingat relatively low gas density, it was assumed that the collisionsleading to ionization are far apart and that a large proportion ofthe molecules breaks up under these conditions yielding to at leastone fragment which is neutral or in charge state 1+, so that there isno or only a small electrostatic repulsion. Therefore, it was consid-ered that the dissociation of BeO molecules would not significantlyaffect the beam size [1].

In order to estimate the effect of the Coulomb explosion in theexperiments at ASTER and to determine how the beam profiles canbe affected by the coulomb explosion, a simple model was used. Itwas assumed that the molecule breaks up in the ground state, witha bond length of about 0.13 nm as given for a neutral BeO molecule[14]. In addition, an isotropic molecular orientation is considered.The charges of the fragments are concentrated at their centersand this potential energy is then converted into kinetic energy.Finally, the velocity vector of the fragments has to be added tothe velocity of the molecule in the stripper (this procedure is de-scribed in the appendix of [11]). An initial beam width in the rangeof that determined for Cl was also assumed as well as an energystraggling in the stripper. Initially, only break-up products ofcharge state 0 and 1 have been considered, but the induced effectswere too small to explain the experimental results. Therefore con-tributions of break-up products of charge state 2 (qBe = 1 and qO = 2or qBe = 2 and qO = 1) and 4 (qBe = 2, qO = 2) were included in the

5 10ion (mm)

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0

0.1

0.2

0.3

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10BExperimentGaussian fit

(c)

normal distributions fitted to the central part of the peaks (dashed line). Regardingbutions, are evidenced. Regarding 9Be (b) and 10B (c), significantly wider (r ffi 1.7–utions and on both sides additional tails are observed. They can be attributed to the

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Be+ (stripper = 5.2x10-4 mb)ExperimentModel

(c)

Fig. 2. Beam profiles under various gas stripper pressure conditions: (a) 9Be++ profiles under normal operating conditions (gas stripper pressure: 1.3 � 10�2 mbar), as shownin Fig. 1, (b) low gas stripper pressure (5.2 � 10�4 mbar), and (c) 9Be+ at low gas stripper pressure. The effect of the Coulomb explosion is more pronounced at low pressures,because then the ions ending up in the selected charge state are predominantly produced by a direct molecular break-up with ionization into the final charge state. Thecontributions of various charge states to the coulomb explosion were estimated by model calculations (dashed line).

Table 1Contribution of the various charge products to the coulomb explosion needed for thereconstruction of the beam profiles shown in Fig. 2.

q1 � q2 Be++ (%) Be++ (low pressure) (%) Be+ (low pressure) (%)

0 29 27 501 39 29 402 10 4 64 22 40 4

E. Nottoli et al. / Nuclear Instruments and Methods in Physics Research B 294 (2013) 397–402 399

model. The contributions of the various charge state products weremanually adjusted until a good agreement between theoretical andexperimental profiles was reached (Fig. 2). The correspondingcontributions are given in Table 1. According to the work of B.Hartmann et al. [11], the effect of the Coulomb explosion is morepronounced at very low stripper pressure, because in these condi-tions the ions ending up in the selected charge state are predomi-nantly produced by a direct molecular break-up with ionizationinto the final charge state. This was also confirmed at ASTER(Fig. 2, Table 1).

The data presented in Table 1 show that a considerable fraction(�30%) of the molecules have to break up into charge state prod-ucts 2 and 4 in order to produce the large tails which were ob-served in the experiments. In totality, about 70% of the moleculesbreak up into charged fragments under normal stripper pressure.The data given in Table 1 should however be considered with cau-tion. The reality is more complex and other processes not includedin the model may play a role, e.g. the molecules can be in excitedstates before breaking up. Similarly, the bond length depends onthe charge of the molecule just before breaking up. But, based onthe present experiments, we can conclude that the effect ofcoulomb explosion in the dissociation of BeO molecules cannotbe ignored even with gas stripping and has to be taken into ac-count in the design of new AMS facilities as well as for optimizingthe performance of existing ones.

4. Energy loss and straggling

The background suppression depends strongly on the energydifference between the two isobars after the foil as well as onthe energy straggling introduced during the stopping process with-in the foil. The energy loss difference is determined by the stoppingpower, which can be estimated using programs (SRIM [15], MSTAR[16]), which are available from the internet, using tables(Northcliffe [17]) or using semi-empirical formulas (Weijers[18]). In addition computer codes have been developed, which relyon basic principles such as PASS [19] and CasP [20]. All these meth-ods typically give reasonable results for the energy loss, withuncertainties of a few percent, but the differences in energy loss

of two isobars, such as Cl–S, are small compared to the total energyloss and, therefore, the error associated to the calculated differencecan be relatively large. For the energy straggling, it is more difficultto make reliable predictions. The SRIM program can make simula-tions in which a generated transmit file allows derivation of energystraggling information, which is often used for estimating theenergy straggling. However, the SRIM code essentially followsthe Bohr formula, which predicts an energy straggling that onlydepends on the projectile, target atomic number and the foil thick-ness. For silicon nitride foils, this energy straggling was measuredat ETH for various projectiles (zp = 4–26) in the energy range of0.4–2 MeV showing that the straggling is significantly smaller thangiven by the Bohr formula or the SRIM calculations [21]. In the en-ergy range in which the facility ASTER is operating the straggling isexpected to be larger than the Bohr predictions. All these factswere the motivation to measure also energy loss and stragglingat ASTER under the same conditions as the AMS measurementsare normally performed. The ESA serves as the energy measuringdevice, but also the lenses and magnet were tuned for optimaltransmission to the detector. An ESA voltage scan was used todetermine the energy straggling.

The energy loss and straggling information are compared withmodels, the experimental data being converted to a mean stoppingpower (dE/dx) in MeV/mg/cm2 by using a density of 3.1 g/cm3 [21].For the model calculations a composition of Si3N3.1 was assumed. Itwas determined on similar foils from the same manufacturer by HeRutherford back scattering at 2 MeV [21]. Because uncertainties infoil thickness and density have to be propagated when estimatingthe stopping power, stopping power ratios independent of thick-ness and densities are also given in Figs. 3 and 4. For 10Be and10B (Fig. 3), the stopping powers derived from the various modelsagree within a few percent in the region of interest (10–12 MeV),except for those obtained using the Weijers formula. The experi-mental results are slightly larger than the average predicted bythe models. This could be explained by the uncertainties associatedto the thickness and/or the density. The relative difference in stop-ping power being quite large (45%), the degrader foil method pro-vides a good isobar separation for B–Be. All the models but MSTARprovide reasonable predictions for the stopping power ratio. Atlower energies (2–5 MeV), the models give quite contradictory re-sults, so that no reasonable predictions can be made.

For Cl (Fig. 4), the stopping powers from the various modelsvary within a range of 10% and the stopping power ratios are quitescattered. It is therefore almost impossible to make reliable predic-tions for the isobar separation. The experimentally determined dif-ference in the stopping power of 36Cl and 36S is about 7.3% andSRIM predicts about 4%. The energy straggling data for B, S andCl are summarized in Fig. 5, with the predictions of the Bohrformula [22] and Yang model [23]. The experimental data are inreasonable agreement with the curves obtained with the Yang-

0 4 8 12Energy (MeV)

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1.2

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1.4

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1.5(b)

Fig. 3. Stopping powers for 10Be and 10B calculated using various methods [15–19]and comparison with the experimental results of this work (a). Reasonableagreement was found between models and the experiment. The ratios in stoppingpower are independent of errors in the thickness of the foil (b).

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1

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1.1(b)

Fig. 4. Stopping power curves of the various predictions [15–19] for 36S and 36Cl (a).The stopping power ratios (b) of the various models for 36Cl and 36S exhibit suchlarge deviations that it is very difficult to make any reasonable prediction for thepeak separation. The SRIM program gives the largest deviation from the experi-mental point measured in this work.

400 E. Nottoli et al. / Nuclear Instruments and Methods in Physics Research B 294 (2013) 397–402

formula, as also found at much lower energies. These resultsclearly show the present situation, which does not allow accuratepredictions for the isobar separation.

5. Charge state distributions for 35Cl

The proportion of particles which can be detected is strongly re-lated to the charge state distribution. For charge state distributionsof ions passing though foils or gases, a considerable number ofexperimental data are available [24,25] and various semi-empiricalformula to describe the distribution based on mean charge andbeam width are available, especially for carbon foils [26]. But sincesome dependences on target composition have been reported[27,28], it was not clear to what extent the data obtained from car-bon foils can be transposed to silicon nitride foils. Therefore, chargestate distributions from the ASTER silicon nitride foil were deter-

mined experimentally for Cl. The ESA and magnet behind the sili-con nitride foil were used as charge state selecting device. Thebeam intensities were reduced in order to avoid damaging thefoils. One charge state after the other was tuned to the Faradaycup in front of the detector. In between these measurements, thebeam intensity without the foil was monitored. The charge statedistributions were measured for initial energies of 30 MeV (5+)and 24 MeV (4+) leading to final energies of 23.9 and 19.8 MeV,respectively. Based on these measurements, charge state distribu-tions were calculated, assuming that losses due to angular and en-ergy straggling are independent of the final charge state. Then thecalculated proportions were normalized such that their sum equals100%. The distributions shown Fig. 6 are well described by normaldistributions, the corresponding widths and positions being givenin Table 2.

0 10 20 30 40Energy (MeV)

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gglin

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B

SCl

Cl

Cl

S

S

B

Be

Fig. 5. For 10B and 37Cl, the experimentally determined energy straggling in the foilis compared with the Bohr-Straggling and with formula of Yang et al. [23].

6 8 10 12 14Charge state

0

10

20

30

40

Yiel

d (%

)

19.8 keV23.9 keV

Fig. 6. Normalized charge state distributions for 35Cl at 23.9 and 19.8 MeV asfunction of the charge state. The distributions can be well described by normaldistributions characterized by the mean charge qm and the width r (See Table 2).

Table 2Fit parameters (position qm and width r (standard deviation)) of the normaldistributions describing charge state intensities given in Fig. 6.

E (MeV) 19.8 23.9qm 9.45 10.07r 1.16 1.18Transmission (%) 53.4 62.4

E. Nottoli et al. / Nuclear Instruments and Methods in Physics Research B 294 (2013) 397–402 401

A width of about 1.16 corresponds to a maximum yield of 34%.Therefore, even under optimal selection of the energy, no morethan 34% transmission through the foil can be obtained, meaningthat the foil method will always lead to an intensity reduction ofa factor of 3. For the initial energy of 30 MeV, the sum of non nor-malized charge states adds up to 62.2% and the sum for the lowerenergy is 53.4%. These intensity losses are primarily due to the

angular straggling in the foil. Ion optics calculations using theETH optics [29], the initial angular distribution from a SRIM simu-lation and considering the limitations given by the lay-out lead to atransmission of 65% for the higher energy. This value is very closeto the experimental value indicating that angular distribution isquite well described by SRIM.

6. Consequences of these results on the performance of thedegrader foil method

The data presented and discussed in this paper allow betterunderstanding the performances of the degrader foil method. Con-sidering 10Be measurements, a transmission to the detector of 22%and background levels significantly lower than 10–15 are evidenced[9,10]. Only a few AMS laboratories reported higher yields. The bor-on separation in the working energy range is very satisfactory, thetwo peaks being separated by �370 keV and the energy stragglingfor B and Be being in the range of 60–75 keV (FWHM). Theoreticalestimation of a boron suppression factor is difficult because the iso-bar profiles might differ from a simple Gaussian distribution due tolow and high energy tails caused by scattering or charge changingprocesses. Nevertheless, it seems that sufficient boron suppressioncould be obtained using foils 10–20% thinner, which would increasethe transmission by 5–10%. Due to the coulomb explosion the beamis relatively large, causing an additional beam loss. A rectangularfoil and aperture with a size of 12 � 8 mm would probably allowan additional transmission improvement.

Regarding Cl measurements, the degrader foil method providesisobar suppression of a few hundred [9]. This can be understoodconsidering the isobar separation of �420 keV, the energy strag-gling as given in Fig. 6 for a slit setting at (±3 mm), and the disper-sion of the ESA. A transmission from the foil to the detector of�14% has been reported [10]. This can be assigned to the followingeffects: foil stripping yield to charge state 10+ (33%), transmissionto the detector based on angular scattering (62%) (Table 2), and theeffect of the energy straggling in the foil (68%). This last value isestimated from the energy straggling, the dispersion of the ESAand the slits settings in front of the detector. These losses due tothe energy straggling have been reduced by asymmetric slits set-tings in front of the detector (+3,�5 mm), leading to an 11–13%higher overall transmission. On the side of the S peak the slit cannot be opened, because this would have reduced the backgroundsuppression.

The use of charge state 4+ would be an other option to increasethe yield significantly (factor of �2). On the other hand, this wouldreduce the transmission due to angular straggling (53% transmis-sion). It would also reduce the isobar separation in the foil, but thiswould be compensated to a large extend by a smaller energy strag-gling (Fig. 6). In addition, less energy would be available in thedetector for particles identification.

7. Conclusions

This study clearly shows that the available models or semi-empirical formulas do not presently allow precisely predicting iso-bar suppressions using specific arrangements and estimatingyields. Reasonable good models are however available for small an-gle scattering. The simulation program SRIM as well as analyticalmethod such as the scattering formulas based on Lindhard’s [30]scattering theories, which have been expanded for multiple scat-tering by Sigmund and Winterbon [31] give reliable results. Firstestimates can be made for stripping yields using semi-empiricalformulas while mean charge and width give reasonable informa-tion about most intense charge states. It is much more difficultto get reliable predictions for the isobar separation, especially for

402 E. Nottoli et al. / Nuclear Instruments and Methods in Physics Research B 294 (2013) 397–402

heavier ions. The difference in the stopping power can be wrong byalmost a factor of two as shown for the Cl–S separation. For the en-ergy, the Bohr energy straggling formula as well as SRIM simula-tion can be far off, better estimates being obtained with themethod given by Yang et al.

Designing an analyzing system with electrostatic and magneticdeflection behind the foil is easier at low energies, because rela-tively small unit with large deflection can be built that also pro-vides the required focusing. In the energy range in which theASTER facility is operating, relatively large deflection units withlarge radii and smaller deflection angles are used so that additionof focusing elements are needed. Acceptance angles are limitedleading to large scattering losses. Therefore the new 6 MV AMSfacility at Cologne [32] is using another system with only one anal-ysis magnet with large deflection (120�), a high dispersion and alsoa much higher angular acceptance (30 mrad), providing essentially100% transmission.

For 10Be analysis, a satisfactory boron suppression with a rea-sonable yield is obtained. However the absorber method usingcharge state 3+ can provide about 20% higher yields at an accelera-tor having also a maximum terminal voltage of 5 MV. For 36Cl anal-ysis, while a very good isobar suppression is also provided, the yieldis quite low compared to other facilities. In the last decade, signifi-cant progress has been made in isobar separation using gas coun-ters. The AMS laboratories SUERC [33] (30 MeV, 5 MV, 5+) andVERA [34,35] (24 MeV,3 MV, 7+) have demonstrated that withouta degrader foil low background (36Cl/Cl > 10�15) can be obtainedwith much higher yields (4–10 times larger), which makes measur-ing time much shorter and more efficient. Such high yields willnever be possible with the degrader foil technique. On the otherhand, the system at ASTER provides a better sulfur suppression.Sample preparation and pressing into holders are then simpler.

Here, the first quantitative results on the coulomb explosion ofBeO in gas stripping are reported, indicating that this effect can beessential for beam losses and has to be considered in the design ofnew AMS systems. More experimental work is needed in order tobetter understand this dissociation process. Dedicated experi-ments have to be performed to obtain more detailed and more pre-cise information on the most relevant dissociation channels(charge states of the fragments, angular distribution).

Acknowledgements

We thank Peter Sigmund for providing stopping power data cal-culated with the PASS code. The ASTER AMS national facility (CER-EGE, Aix en Provence) is supported by the INSU/CNRS, the FrenchMinistry of Research and Higher Education, IRD, and CEA.

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