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![(Color) Beam cleaning measurements for six different 316 LN stainless steel vacuum chambers continuously bombarded with 1 : 5 10 9 Pb 53 ions (per shot) under 89 : 2 grazing incidence. The result for the Pd coating (L) and the St707 getter strips (K) are compared with the Ag (I#3) and Au (E#3) coatings. For comparison, the scrubbing of the previously studied NEG coating (C) and the LEAR-type vacuum chamber (A) are also shown [4].](profile/Detlef-Kuechler/publication/46101191/figure/fig5/AS:276965450895365@1443045117308/Color-Beam-cleaning-measurements-for-six-different-316-LN-stainless-steel-vacuum.png)
(Color) Beam cleaning measurements for six different 316 LN stainless steel vacuum chambers continuously bombarded with 1 : 5 10 9 Pb 53 ions (per shot) under 89 : 2 grazing incidence. The result for the Pd coating (L) and the St707 getter strips (K) are compared with the Ag (I#3) and Au (E#3) coatings. For comparison, the scrubbing of the previously studied NEG coating (C) and the LEAR-type vacuum chamber (A) are also shown [4].
Source publication
The ion-induced desorption experiment, installed in the CERN Heavy Ion Accelerator LINAC 3, has been used to measure molecular desorption yields for 4.2 MeV/u lead ions impacting under grazing incidence on different accelerator-type vacuum chambers. Desorption yields for H2, CH4, CO, and CO2, which are of fundamental interest for future accelerator...
Contexts in source publication
Context 1
... , was found to be larger for the Au coated chamber than for all other vacuum chambers studied so far at LINAC 3. We currently have no sound explanation for this experimental observation. The measured pressure rise and beam scrubbing of chamber F, which was etched and vacuum fired at 950 , is displayed in Fig. 4. An effective desorption yield of about 7600 molecules = ion was measured at the beginning of the scrubbing run, a yield very close to the value obtained with chamber I#1, which was also etched but vacuum fired at 1050 . After 100 h heavy-ion bombardment of chamber F the molecular desorption decreased by a factor of 170 . In conclusion, there is no benefit to vacuum fire accelerator-type stainless steel vacuum chambers at 1050 C , instead of the normally used 950 C , in order to decrease the effective ion-induced desorption yield. In Fig. 5 the scrubbing results for the Pd sputter coated vacuum chamber L and the St707 getter strips are compared with the Ag and the Au coated chambers. For comparison, the previously obtained results for a nonevaporable getter (NEG) coated (TiZrV) vacuum chamber, that was activated first at 200 C and later at 300 C [4], are also shown in Fig. 5 together with the scrubbing of the LEAR-type vacuum chamber A [4]. The measured pressure increase for the Pd coating and the getter strips were about 2 orders of magnitude lower than for the unpolished/ uncoated stainless steel vacuum chamber. The reduced dynamic pressure rise of the Pd film was found to be identical with that of the NEG coating which was activated at 200 C for 24 h (see Fig. 5). The heavy-ion-induced molecular desorption of the St707 getter was found to be very similar to the sputter coated Pd film. During beam scrubbing of the Pd surface a pressure fluctuation was observed after 15 h, which became less pronounced after 40 h of continuous ion bombardment. This pressure fluctuation, also observed for the getter strips, the Au coated and some other vacuum chambers, remains unexplained for the moment. At the beginning of each scrubbing run the total pressure increase P , due to continuous (every 1.2 s) bombardment with Pb 53 ions under 89 : 2 grazing incidence, was measured. In Fig. 6 the results obtained during this study (5 chambers, 9 surfaces) and a previously published paper (5 chambers, 6 surfaces) [4] are summarized. It is demon- strated that the large pressure rises of either bare or glow discharged 316 LN stainless steel vacuum chambers was reduced by means of electropolishing or chemical ...
Context 2
... , was found to be larger for the Au coated chamber than for all other vacuum chambers studied so far at LINAC 3. We currently have no sound explanation for this experimental observation. The measured pressure rise and beam scrubbing of chamber F, which was etched and vacuum fired at 950 , is displayed in Fig. 4. An effective desorption yield of about 7600 molecules = ion was measured at the beginning of the scrubbing run, a yield very close to the value obtained with chamber I#1, which was also etched but vacuum fired at 1050 . After 100 h heavy-ion bombardment of chamber F the molecular desorption decreased by a factor of 170 . In conclusion, there is no benefit to vacuum fire accelerator-type stainless steel vacuum chambers at 1050 C , instead of the normally used 950 C , in order to decrease the effective ion-induced desorption yield. In Fig. 5 the scrubbing results for the Pd sputter coated vacuum chamber L and the St707 getter strips are compared with the Ag and the Au coated chambers. For comparison, the previously obtained results for a nonevaporable getter (NEG) coated (TiZrV) vacuum chamber, that was activated first at 200 C and later at 300 C [4], are also shown in Fig. 5 together with the scrubbing of the LEAR-type vacuum chamber A [4]. The measured pressure increase for the Pd coating and the getter strips were about 2 orders of magnitude lower than for the unpolished/ uncoated stainless steel vacuum chamber. The reduced dynamic pressure rise of the Pd film was found to be identical with that of the NEG coating which was activated at 200 C for 24 h (see Fig. 5). The heavy-ion-induced molecular desorption of the St707 getter was found to be very similar to the sputter coated Pd film. During beam scrubbing of the Pd surface a pressure fluctuation was observed after 15 h, which became less pronounced after 40 h of continuous ion bombardment. This pressure fluctuation, also observed for the getter strips, the Au coated and some other vacuum chambers, remains unexplained for the moment. At the beginning of each scrubbing run the total pressure increase P , due to continuous (every 1.2 s) bombardment with Pb 53 ions under 89 : 2 grazing incidence, was measured. In Fig. 6 the results obtained during this study (5 chambers, 9 surfaces) and a previously published paper (5 chambers, 6 surfaces) [4] are summarized. It is demon- strated that the large pressure rises of either bare or glow discharged 316 LN stainless steel vacuum chambers was reduced by means of electropolishing or chemical ...
Context 3
... , was found to be larger for the Au coated chamber than for all other vacuum chambers studied so far at LINAC 3. We currently have no sound explanation for this experimental observation. The measured pressure rise and beam scrubbing of chamber F, which was etched and vacuum fired at 950 , is displayed in Fig. 4. An effective desorption yield of about 7600 molecules = ion was measured at the beginning of the scrubbing run, a yield very close to the value obtained with chamber I#1, which was also etched but vacuum fired at 1050 . After 100 h heavy-ion bombardment of chamber F the molecular desorption decreased by a factor of 170 . In conclusion, there is no benefit to vacuum fire accelerator-type stainless steel vacuum chambers at 1050 C , instead of the normally used 950 C , in order to decrease the effective ion-induced desorption yield. In Fig. 5 the scrubbing results for the Pd sputter coated vacuum chamber L and the St707 getter strips are compared with the Ag and the Au coated chambers. For comparison, the previously obtained results for a nonevaporable getter (NEG) coated (TiZrV) vacuum chamber, that was activated first at 200 C and later at 300 C [4], are also shown in Fig. 5 together with the scrubbing of the LEAR-type vacuum chamber A [4]. The measured pressure increase for the Pd coating and the getter strips were about 2 orders of magnitude lower than for the unpolished/ uncoated stainless steel vacuum chamber. The reduced dynamic pressure rise of the Pd film was found to be identical with that of the NEG coating which was activated at 200 C for 24 h (see Fig. 5). The heavy-ion-induced molecular desorption of the St707 getter was found to be very similar to the sputter coated Pd film. During beam scrubbing of the Pd surface a pressure fluctuation was observed after 15 h, which became less pronounced after 40 h of continuous ion bombardment. This pressure fluctuation, also observed for the getter strips, the Au coated and some other vacuum chambers, remains unexplained for the moment. At the beginning of each scrubbing run the total pressure increase P , due to continuous (every 1.2 s) bombardment with Pb 53 ions under 89 : 2 grazing incidence, was measured. In Fig. 6 the results obtained during this study (5 chambers, 9 surfaces) and a previously published paper (5 chambers, 6 surfaces) [4] are summarized. It is demon- strated that the large pressure rises of either bare or glow discharged 316 LN stainless steel vacuum chambers was reduced by means of electropolishing or chemical ...
Citations
... achieving UHV and XHV conditions. The fundamental properties of the NEG films that enable the fulfillment of these conditions are low thermal outgassing rate, 2,3 low ion-stimulated desorption yield, 13 low electron-stimulated desorption (ESD) yield, 14 uniformly distributed pumping speed, 15,16 low activation temperature, 2,17,18 and low secondary electron yield (SEY). 19,20 In addition, NEG films allow for the evacuation of residual gases from vacuum chambers without the necessity of any additional equipment. 1 Following the introduction of NEG films, binary combinations of column IV B elements such as Ti-Hf, Ti-Zr, and Hf-Zr were examined. ...
The performance of next-generation particle accelerators has been adversely affected by the occurrence of electron multipacting and vacuum instabilities. Particularly, minimization of secondary electron emission (SEE) and reduction of surface resistance are two critical issues to prevent some of the phenomena such as beam instability, reduction of beam lifetime, and residual gas ionization, all of which occur as a result of these adverse effects in next-generation particle accelerators. For the first time, novel quinary alloy Ti–Zr–V–Hf–Cu non-evaporable getter (NEG) films were prepared on stainless steel substrates by using the direct current magnetron sputtering technique to reduce surface resistance and SEE yield with an efficient pumping performance. Based on the experimental findings, the surface resistance of the quinary Ti–Zr–V–Hf–Cu NEG films was established to be 6.6 × 10⁻⁷ Ω m for sample no. 1, 6.4 × 10⁻⁷ Ω m for sample no. 2, and 6.2 × 10⁻⁷ Ω m for sample no. 3. The δmax measurements recorded for Ti–Zr–V–Hf–Cu NEG films are 1.33 for sample no. 1, 1.34 for sample no. 2, and 1.35 for sample no. 3. Upon heating the Ti–Zr–V–Hf–Cu NEG film to 150 °C, the XPS spectra results indicated that there are significant changes in the chemical states of its constituent metals, Ti, Zr, V, Hf, and Cu, and these chemical state changes continued with heating at 180 °C. This implies that upon heating at 150 °C, the Ti–Zr–V–Hf–Cu NEG film becomes activated, showing that novel quinary NEG films can be effectively employed as getter pumps for generating ultra-high vacuum conditions.
... Since its invention at CERN [1][2][3][4][5][6][7][8], the non-evaporable getter (NEG) coating has been successfully applied to inner surfaces of many vacuum chambers of particle accelerators [9][10][11][12][13][14][15][16][17][18][19][20][21]. NEG coating acts as a diffusion barrier between vacuum chamber material and vacuum resulting in a reduction of the electron, photon and ion stimulated desorption yields. ...
Non-evaporable getter (NEG) coating is widely used for vacuum system of charged particle accelerators. The RF surface resistance of NEG coating is increasing with its thickness. Therefore, knowing how NEG coating properties depend on its thickness is essential for vacuum system design of accelerators. This paper describes the results of studying the pumping properties of Ti-Zr-V NEG films deposited from an alloy target for thicknesses in the range between 0.1 and 1μm. Good pumping properties for H2 and CO have been demonstrated after activation to 140 °C. It has been demonstrated that initial CO sticking probability does not depend on thickness, however, initial H2 sticking probability and CO sorption capacity are almost proportional to NEG thickness. The NEG coating degradation with a number of activations has been observed, the thinner NEG film the stronger the degradation.
... On one hand, to reduce the ultimate pressure and vacuum gradient as well as maintain the vacuum stability in accelerators, non-evaporable getter (NEG) films such as Ti-Zr-V films [1][2][3] have been deposited on the inner surface of the vacuum pipes or getter pumps in vacuum systems [2,4], thanks to their distributed pumping properties [3,[5][6][7]. On the other hand, to suppress electron clouds in vacuum pipes, various solutions, such as the laser ablation technique [8], artificially grooving surfaces [9], carbon coatings [10] and TiN films [11], etc., have been developed. ...
... On one hand, to reduce the ultimate pressure and vacuum gradient as well as maintain the vacuum stability in accelerators, non-evaporable getter (NEG) films such as Ti-Zr-V films [1][2][3] have been deposited on the inner surface of the vacuum pipes or getter pumps in vacuum systems [2,4], thanks to their distributed pumping properties [3,[5][6][7]. On the other hand, to suppress electron clouds in vacuum pipes, various solutions, such as the laser ablation technique [8], artificially grooving surfaces [9], carbon coatings [10] and TiN films [11], etc., have been developed. ...
Secondary electron emission (SEE) inhibition and vacuum instability are two important issues in accelerators that may induce multiple effects in accelerators, such as power loss and beam lifetime reduction. In order to mitigate SEE and maintain high vacuum simultaneously, open-cell copper metal foam (OCMF) substrates with Ti-Zr-V-Hf non-evaporable getter (NEG) coatings are first proposed, and the properties of surface morphology, surface chemistry and secondary electron yield (SEY) were analyzed for the first time. According to the experimental results tested at 25 °C, the maximum SEY (δmax) of OCMF before and after Ti-Zr-V-Hf NEG film deposition were 1.25 and 1.22, respectively. The XPS spectra indicated chemical state changes of the metal elements (Ti, Zr, V and Hf) of the Ti-Zr-V-Hf NEG films after heating, suggesting that the NEG films can be activated after heating and used as getter pumps.
... The main tendencies of ion stimulated desorption, in regard to desorbed species and intensities, correlate well with ESD [21]. A special case of ion stimulated desorption is represented by high energy (MeV/nucleon) highly ionized heavy ions [37]. This phenomenon is particularly important for ion storage rings where the impact of lost ions can induce pressure bursts. ...
Principles of the precision cleaning dedicated to ultra-high vacuum applications are reviewed together with the techniques for the evaluation of surface cleanliness. Methods to verify the effectiveness of cleaning procedures are addressed. Examples are presented to illustrate the influence of packaging and storage on the recontamination of the surface after cleaning. Finally, the effect of contamination on some relevant surface properties, such as secondary electron emission and wettability, is presented. This article is an updated and shortened version of the one previously published for the CAS school on the vacuum of accelerators 2006.
... Compared with the δ max of Ti-Zr-V getter film which has been widely used in many accelerators, such as Large Hadron Collider (LHC) [37,38], the High Energy Accelerator Research Organization (KEK) B-Factory [39] etc., that of as-received Ti-Zr-V getter film with aluminum alloy substrates was about 2.10 with the δ max at 300 eV [40]. This indicates that the E max of Ti-V-Hf-Zr getter film is lower than that of Ti-Zr-V film with aluminum alloy substrates. ...
For improving the vacuum and mitigating the electron clouds in ultra-high vacuum chamber systems of high-energy accelerators, the deposition of Ti-V-Hf-Zr getter film on a laser-treated aluminum alloy substrate was proposed and exploited for the first time in this study. The laser-treated aluminum surface exhibits a low secondary electron yield (SEY), which is even lower than 1 for some selected laser parameters. Non-evaporable getter (NEG) Ti-V-Hf-Zr film coatings were prepared using the direct current (DC) sputtering method. The surface morphology, surface roughness and composition of Ti-V-Hf-Zr getter films were characterized and analyzed. The maximum SEY of unactivated Ti-V-Hf-Zr getter film on laser-treated aluminum alloy substrates ranged from 1.10 to 1.48. The X-ray photoelectron spectroscopy (XPS) spectra demonstrate that the Ti-V-Hf-Zr coated laser-treated aluminum alloy could be partially activated after being heated at 100 and 150 °C, respectively, for 1 h in a vacuum and also used as a pump. The results were demonstrated initially and the potential application should be considered in future particle accelerators.
... H 2 and CO are main residual gases for vacuum system of particle accelerators [5,[13][14][15] where the gas load is mainly from material thermal outgassing. Also in a desorption rate experiment [16][17][18][19], H 2 and CO are two dominating gas species when ions with a certain energy bombard stainless steel or copper. Therefore the test gases selected are H 2 and CO. ...
HIAF-BRing, a new multi-purpose accelerator facility of the High Intensity Heavy-Ion Accelerator Facility project, requires an extremely high vacuum lower than 10⁻⁹ Pa to fulfill the requirements of radioactive beam physics and high energy density physics. Use of large speed Titanium sublimation pump (TSP) in combination with Sputter ion pumps (SIP) is not always feasible due to space limitations. A novel combination pump, based on Non Evaporable getter (NEG) and a 10 l/s SIP (NEXTorr® D 2000-10) has been evaluated as it provides large speed in a more compact design. The two combination pumps (TSP + SIP and NEXTorr D 2000-10) have been tested by dynamic flow method to measure the ultimate pressure, the pumping speed and the suitability for HIAF. Test results show that both combination pumps can be used in the pressure range of 10⁻¹⁰ Pa. The ultimate pressure of TSP + SIP combination pump is slightly lower than NEXTorr D 2000-10, but the latter one has much larger sorption capacities (H2: 210200 Pa l vs 265 Pa. l; CO: 430 Pa. l vs 24 Pa. l), which means it is applicable to a wider pressure range. At the same time, after twenty activation cycles, the initial pumping speed of NEXTorr D 2000-10 for H2 and CO decreased less than 10% as compared with the initial pumping speed of the first activation, which meets the actual vacuum system requirement of HIAF. A dedicated vacuum chamber with collimator and NEXTorr D 2000-10 has been designed and manufactured to stabilize the dynamic vacuum by decreasing the heavy ion induced gas desorption and increasing the gas pumping speed. The static and dynamic vacuum pressure evolution has been simulated to verify the feasibility of the NEXTorr D 2000-10 used in the HIAF-BRing.
... Titanium-Zirconium-Vanadium (TiZrV) as one of nonevaporable getters (NEGs)1234 has been extensively studied during the past two decades for low secondary electron yield567 and their sorption properties toward many gases such as hydrogen, oxygen, nitrogen, carbon monoxide and dioxide. The sorption of these gases except H2 is not reversible and it causes a progressive contamination for TiZrV film [1, 8, 9]. Moreover, repeated air exposure–activation cycles progressively enrich the film with reactive gases, reducing its performance and shortening its ...
TiZrV film is mainly applied in the ultra-high vacuum pipe of storage ring.
Thin film coatings of palladium which was added onto the TiZrV film to increase
the service life of nonevaporable getters and enhance pumping speed for H2, was
deposited on the inner face of stainless steel pipes by dc magnetron sputtering
using argon gas as the sputtering gas. The TiZrV-Pd film properties were
investigated by atomic force microscope (AFM), scanning electron microscope
(SEM), X-ray photoelectron spectroscopy (XPS) and X-Ray Diffraction (XRD). The
grain size of TiZrV and Pd film were about 0.42~1.3 nm and 8.5~18.25 nm
respectively. It was found that the roughness of TiZrV films was small, about
2~4 nm, for Pd film it is large, about 17~19 nm. PP At. % of Pd in TiZrV/Pd
films varied from 86.84 to 87.56 according to the XPS test results.
... Desorption yield measurements at cryogenic temperatures are motivated by the design of future heavy-ion accelerators, for example, SIS100, which is part of the GSI FAIR (Facility for Antiproton and Ion Research) project [6], and the operation of the Large Hadron Collider (LHC). Two different targets were chosen for our studies at HLI; the first material is gold-coated copper, which has already been investigated at ambient and cryogenic temperatures [5,7]. Such gold coatings are of special interest because they are part of the baseline design for the SIS100 cryocatcher [8]. ...
... On the other hand, this discrepancy between the HLI and LINAC 3 desorption results is not surprising, since it is very well known that the amount of surface impurities, especially adsorbed carbon and oxygen, plays a significant role on the absolute values of eff [11]. This argument may be supported by the different experimental conditions, e.g., the sample storage time in air and the bakeout temperature difference between the two experiments, which both can influence the amount of adsorbed carbon and oxygen on gold surfaces [7]. At 77 K the desorption yield difference for the two Au=Cu targets, bombarded with 1:4 MeV=u Xe 18þ ions and 4:2 MeV=u Pb 54þ ions, increases to %61% (see Fig. 8). ...
Heavy-ion-induced desorption of two different cryogenic targets was studied with a new experimental setup installed at the GSI High Charge State Injector. One gold-coated and one amorphous-carbon-coated copper target, bombarded under perpendicular impact with 1.4 MeV/u Xe18+ ions, were tested. Partial pressure rises of H2, CO, CO2, and CH4 and effective desorption yields were measured at 300, 77, and 8 K using continuous heavy-ion bombardment. We found that the desorption yields decrease with decreasing target temperature and measured the yield rises as a function of CO gas cryosorbed at 8 K. In this paper we describe the experimental system comprising a new cryogenic target assembly, the preparation of the targets, the test procedure, and the evaluation of the effective pumping speed of the setup. Pressure rise and gas adsorption experiments are described; the obtained results are discussed and compared with literature data.
... The results obtained in previous studies have clearly shown that the heavy-ion induced desorption yield of the studied technical surfaces strongly depends on the surface properties of the targets. The amount of carbon and oxygen plays an important role since less surface adsorbates resulted in lower yield values [8]. Therefore, all samples were transferred under vacuum from the SEY instrument to the x-ray photoemission spectroscopy system. ...
During the past decade, intense experimental studies on the heavy-ion induced molecular desorption were performed in several particle accelerator laboratories worldwide in order to understand and overcome large dynamic pressure rises caused by lost beam ions. Different target materials and various coatings were studied for desorption and mitigation techniques were applied to heavy-ion accelerators. For the upgrade of the CERN injector complex, a coating of the Super Proton Synchrotron (SPS) vacuum system with a thin film of amorphous carbon is under study to mitigate the electron cloud effect observed during SPS operation with the nominal proton beam for the Large Hadron Collider (LHC). Since the SPS is also part of the heavy-ion injector chain for LHC, dynamic vacuum studies of amorphous carbon films are important to determine their ion induced desorption yields. At the CERN Heavy Ion Accelerator (LINAC 3), carbon-coated accelerator-type stainless steel vacuum chambers were tested for desorption using 4.2MeV/u Pb54+ ions. We describe the experimental setup and method, present the results for unbaked and baked films, and summarize surface characterizations such as secondary electron yield measurements, x-ray photoemission spectroscopy, and scanning electron microscopy studies. Finally, we present a high-energy scaling of lead-ion induced desorption yields from the MeV/u to GeV/u range.
... The main tendencies of ion-stimulated desorption, as desorbed species and intensities, correlate well with ESD [20]. A special case of ion-stimulated desorption is represented by high-energy (MeV/nucleon), highly ionized heavy ions [34]. This phenomenon is particularly important for ion storage rings where the impact of lost ions can induce pressure bursts. ...
Principles of precision cleaning for ultra high vacuum applications are reviewed together with the techniques for the evaluation of surface cleanliness. Methods to verify the effectiveness of cleaning procedures are discussed. Examples are presented to illustrate the influence of packaging and storage on the recontamination of the surface after cleaning. Finally, the effect of contamination on some relevant surface properties, like secondary electron emission and wettability is presented.
