Construction and Test of a Cryocatcher Prototype for SIS100

The main accelerator SIS100 of the FAIR-complex will provide heavy ion beams of highest intensities. Beam loss due to ionization is the most demanding loss mechanism at operation with high intensity, intermediate charge state heavy ions. A special synchrotron design has been devel- oped for SIS100, aiming for hundred percent control of ion- ization beam loss by means of a dedicated cryogenic ion catcher system. To suppress dynamic vacuum effects, the cryo catcher system shall provide a significantly reduced effective desorption yield. The construction and test of a prototype cryocatcher is a task of the EU-FP-7 workpack- age COLMAT. A prototype test setup, including cryostat has been constructed, manufactured and tested under real- istic conditions with beams from the heavy ion synchrotron SIS18. The design and results are presented

XUV Fluorescence Detection of Laser-Cooled Stored Relativistic Ions

An improved moveable in vacuo XUV fluorescence detection system was employed for the laser cooling of bunched relativistic ( β = 0.47) carbon ions at the Experimental Storage Ring (ESR) of GSI Helmholtzzentrum Darmstadt, Germany. Strongly Doppler boosted XUV fluorescence (∼90 nm) was emitted from the ions in a forward light cone after laser excitation of the 2s–2p transition (∼155 nm) by a new tunable pulsed UV laser system (257 nm). It was shown that the detected fluorescence strongly depends on the position of the detector around the bunched ion beam and on the delay (∼ns) between the ion bunches and the laser pulses. In addition, the fluorescence information could be directly combined with the revolution frequencies of the ions (and their longitudinal momentum spread), which were recorded using the Schottky resonator at the ESR. These fluorescence detection features are required for future laser cooling experiments at highly relativistic energies (up to γ ∼ 13) and high intensities (up to 10 11 particles) of ion beams in the new heavy ion synchrotron SIS100 at FAIR

Status Of The FAIR Synchrotron Projects SIS18 And SIS100

A large fraction of the program to upgrade the existingheavy ion synchrotron SIS18 as injector for the FAIR synchrotron SIS100 has been successfully completed. With the achieved technical status, a major increase of theaccelerated number of heavy ions could be reached. Thenow available performance especially demonstrates thefeasibility of high intensity beams of medium charge stateheavy ions with a sufficient control of the dynamicvacuum and connected charge exchange loss. Two furtherupgrade measures, the installation of additional magneticalloy (MA) acceleration cavities and the exchange of themain dipole power converter, are presently beingimplemented. For the FAIR synchrotron SIS100, theprocurement of all major components with longproduction times has been started. With the delivery andtesting of several pre-series components, the phase ofoutstanding technical reserach and developments could becompleted and the readiness for series productionachieved

Entwicklung und Test eines Kryokollimator-Prototypen zur Kontrolle des dynamischen Vakuums im SIS100

Im Rahmen des FAIR-Projektes (Facility for Antiproton and Ion Research) am GSI Helmholtzzentrum für Schwerionenforschung sollen im supraleitenden Synchrotron SIS100 hochintensive Schwerionenstrahlen erzeugt werden. Dazu werden mittlere, anstelle von hohen Ladungszuständen verwendet, was die Raumladungsgrenze zu höheren Teilchenzahlen verschiebt und gleichzeitig Strahlverluste durch Ionisation in Folien oder Gasstrahlen zur Erhöhung des Ladungszustandes vermeidet. Die größte Herausforderung beim Betrieb mit teilgeladenen Schwerionen ist die Minimierung von Strahlverlusten durch Umladung, welche in Kollision zwischen Strahlionen und Restgasteilchen stattfindet. Solche umgeladenen Strahlionen werden vom umlaufenden Strahl getrennt und gehen auf der Vakuumkammerwand verloren. Bei Auftreffen auf die Kammerwand werden durch ionenstimulierte Desorption große Mengen Gas losgelöst und ein lokaler Druckanstieg hervorgerufen. Dieser erhöht wiederum die Wahrscheinlichkeit für weitere Umladung des Strahls, was eine Selbstverstärkung bis zum völligen Strahlverlust auslöst. Eine der Maßnahmen zur Dämpfung dieses Effektes ist der Einsatz von Umladungskollimatoren. Diese garantieren an den Orten der Strahlverluste senkrechten Einfall auf spezielle, niedrig desorbierende Oberflächen. Die Ionenoptik des SIS100 wurde für den Einsatz von Kollimatoren optimiert. Dadurch können nahezu 100% der Umladungsverluste kontrolliert eingefangen werden. In den Bögen des Synchrotrons befinden sich 60 dieser Kollimatoren zwischen den supraleitenden Quadrupolen in einer kryogenen Umgebung. Gegenstand dieser Arbeit ist die Entwicklung, die Konstruktion und der Test eines kryogenen Kollimator-Prototypen. Das im existierenden Schwerionensynchrotron SIS18 erfolgreich installierte, warme Kollimatorsystem wird in dieser Arbeit mit dem des kryogenen SIS100 verglichen. Es werden verschiedene Messungen mit dem Kollimatorsystem vorgestellt. Ausgehend von den Anforderungen an das neue Kollimatorsystem wird die Auslegung des Kollimatorblocks mit Aufhängung und umgebender kryogener, kupferbeschichteten Vakuumkammer beschrieben. Die kalten Oberflächen der Vakuumkammer dienen als Kryopumpe, welche die desorbierten Gase schnell wieder adsorbiert. Dadurch werden die Verluste durch Umladung so gering wie möglich gehalten. Bei der Planung des Kryokollimators stand eine Minimierung des Druckes auf Strahlachse im Vordergrund. Um den Kryokollimator-Prototypen unter realen Bedingungen zu testen, wurde ein eigener Teststand mit Kryostat entworfen, konstruiert und gebaut. Der Teststand wurde an einem existierenden Strahlzweig der GSI-Beschleunigeranlage installiert. Dort wurde der Kryokollimator-Prototyp mit flüssigem Stickstoff und flüssigem Helium gekühlt und mit Schwerionenstrahlen vom SIS18 getestet. Beim Vermessen des durch Strahleinschlag induzierten Druckanstieges in der kalten Kammer wurde erstmalig ein Anstieg der Desorptionsausbeute mit steigender Strahlenergie beobachtet. Von Raumtemperaturmessungen ist ein Abfallen bekannt. Die Übergangstemperatur von 18 K, unterhalb welcher Wasserstoff adsorbiert wird, konnte während der Messungen mehrfach bestätigt werden. Dies ist für den zuverlässigen Betrieb des SIS100 von entscheidender Bedeutung. Der Kryokollimator-Prototyp erfüllte alle Erwartungen und die Tests liefen sehr zufriedenstellend ab. Eine Serienfertigung für das SIS100 kann beauftragt werden

SIS18 – intensity record with intermediate charge state heavy ions

n order to reach the de­sired in­ten­si­ties of heavy ion beams for the ex­per­i­ments at FAIR, SIS18 and SIS100 have to be op­er­at­ed with in­ter­me­di­ate charge states. Op­er­a­tion with in­ter­me­di­ate charge state heavy ions at the in­ten­si­ty level of about 1011 ions per cycle has never been demon­strat­ed else­where and re­quires a ded­i­cat­ed up­grade pro­gram for SIS18 and a ded­i­cat­ed ma­chine de­sign for SIS100. The spe­cif­ic prob­lems com­ing along with the in­ter­me­di­ate charge state op­er­a­tion in terms of charge ex­change pro­cess­es at col­li­sions with resid­u­al gas atoms, pres­sure bumps by ion in­duced des­orp­tion and cor­re­spond­ing beam loss ap­pears far below the typ­i­cal space charge lim­its. Thus, new de­sign con­cepts and new tech­ni­cal equip­ment ad­dress­ing these is­sues are de­vel­oped and re­al­ized with high­est pri­or­i­ty. The up­grade pro­gram of SIS18 ad­dress­ing the goal of min­i­mum ion­iza­tion beam loss and sta­ble resid­u­al gas pres­sure con­di­tions has been de­fined in 2005. A major part of this up­grade pro­gram has been suc­cess­ful­ly re­al­ized, with the re­sult of a world record in ac­cel­er­at­ed num­ber of in­ter­me­di­ate charge state heavy ions

Cryogenic surfaces in a room temperature SIS18 ion catcher

The existing heavy ion synchrotron SIS18 at GSI will be used as a booster synchrotron for SIS100 at FAIR operation. In order to reach the intensity goals, low charge state heavy ions will be used. Unfortunately, such ions have very high ionization cross sections in collisions with residual gas molecules, yielding in beam loss and pressure rise via ion impact stimulated gas desorption. To reduce the desorption yield, room temperature ion catcher providing low desorption surfaces have been installed. Simulations with cryogenic surfaces show, that their high sticking probability prevents the vacuum system from pressure built-ups during operation with heavy ions. Such, the operation with heavy ion beams can be stabilized at higher heavy ion intensities, than solely with room temperature surfaces. A prototype ion catcher containing cryogenic surfaces has been developed and built. The surfaces are cooled by a commercial cold head, which easily allows this system being integrated into the room temperature synchrotron. The development, laboratory tests, and improvements of this system will be presented

Development of a Cryocatcher-System for SIS100

The main accelerator SIS100 of the FAIR-facility will provide heavy ion beams of highest intensities using inter- mediate charge state heavy ions. Ionization beam loss is the most important loss mechanism, therefore, a special syn- chrotron layout has been developed, which includes a ded- icated cold ion catcher system which provides almost hun- dred percent catching efficiency. Dynamic vacuum effects are suppressed effectively by means of special low desorb- ing surfaces. A prototype of the cryocatcher has been de- veloped, constructed and tested with heavy ion beams from SIS18. It is a workpackage of the EU-FP-7 project COL- MAT. Results from these tests are presented, as well as im- plications for the production of the 60 SIS100 cryocatchers

Room temperature vacuum chamber with cryogenic installations

The FAIR complex at the GSI Helmholtzzentrum will generate heavy ion beams of ultimate intensities. To achieve this goal, low charge states have to be used. However, the probability for charge exchange in collisions with residual gas particles of such ions is much higher than for higher charge states. In order to lower the residual gas density to extreme high vacuum conditions, 65% of the circumference of SIS18 have already been coated with NEG, which provides a high and distributed pumping speed. Nevertheless, nobel and nobel-like components, which have very high ionization cross sections, do not get pumped by this coating. A cryogenic environment at moderate temperatures, i.e. at 50-80 K, provides a high pumping speed for all heavy residual gas particles. The only typical residual gas particle that cannot be pumped at this temperature is hydrogen. With an additional NEG coating the pumping will be optimized for all residual gas particles. The installation of cryogenic surfaces in the existing room temperature synchrotron SIS18 at GSI has been investigated. Measurements on a prototype chamber and simulations of SIS18 with cryogenic surfaces based on these measurements are presented

Development of a Cryocatcher Prototype for SIS100

The main synchrotron SIS100 of the FAIR-facility will be operated with high-intensity intermediate charge state heavy ion beams. In order to assure reliable operation with intermediate charge states, a special synchrotron design, including a catcher system for ionized beam ions had to be developed. Intermediate charge state heavy ions suffer from high cross sections for ionization. Due to the ded- icated synchrotron layout, ions which have been further stripped by collisions with residual gas atoms are caught by the ion catcher system in the cryogenic arcs. The con- struction and test of a cryocatcher prototype at GSI is a workpackage of the EU-FP7 project COLMAT. A proto- type catcher including cryostat will be set-up at GSI to per- form measurements with heavy ion beams of the heavy ion synchrotron SIS18