Sarah aull secondary electron yield of srf materials
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In the quest of new materials for SRF applications, the secondary electron yield (SEY) needs also to be taken into consideration. A high SEY holds the risk that multipacting becomes again a main performance limitation of an SRF cavity. In the worst case, a too high SEY makes a material completely unsuitablefor an RF exposed surface. This talk will discuss general aspects of the role of the surface condition and present SEY measurements on different SRF relevant materials, i.e. MgB2, Nb3Sn and NbTiN.
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Sarah aull surface resistance of a bulk-like nb film
Sarah aull surface resistance of a bulk-like nb film
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Nobody can exclude that the final surpreise must still come.
3 ej fccrf legnaro 2014-10-06
The document discusses plans to form an international collaboration to study future circular colliders at CERN, including a 100 TeV proton-proton collider (FCC-hh), a lepton collider (FCC-ee), and a lepton-hadron collider (FCC-he). It outlines initial parameters and opportunities for the superconducting radio frequency (RF) systems, which will need to provide up to 100 MW of continuous wave power to accelerate beams. Key areas of study for the large-scale FCC RF systems include cavity and cryomodule technology, reliability, efficiency, and operational aspects.
Tesi Master Andrea Camacho Romero
This works deals with the A15 compound synthesis on niobium samples and over the
internal surface of niobium cavities by means of induction heating. Specifically, three compounds were studied: Nb3Ga, Nb3Al and Nb-Al-Ga. As for the preparation of the niobium samples, they were treated with BCP solution in order to polish the surface. The niobium cavities were treated with centrifugal tumbling, BCP solution and high pressure water rising. Subsequent, the samples, or cavities, were placed into an inductor controlling the voltage, time, sample position, temperature, type and pressure of gas used. The highest critical temperature
obtained was 18 K and Tc 0,35 K, in Nb-Al-Ga#1 sample by inductive measurement.
Mapping analysis showed the uniform diffusion of aluminum into the niobium, and the gallium diffuses creating channels into niobium. The composition was measured by EDS obtaining (82±1)% wt. Niobium, (11,3±0,9)% wt. Gallium, (4,7±0,2)% wt. Aluminum and (1,9±0,1)% wt. Oxygen. Finally, RF test confirmed that the cavities obtained after the annealing were normal conductive indicating that the preparation parameters must still be optimized.
Tesi Bachelor Debastiani
In questi ultimi anni i problemi energetici e ambientali hanno favorito lo sviluppo di un nuovo settore della ricerca riguardo la produzione di energia pulita sfruttando fenomeni naturali. L'attenzione dei ricercatori è stata catturata dalla possibilità di convertire l'energia solare luminosa
in energia elettrica. Questo processo di conversione, nato nella prima metà del XX secolo, permette di produrre correnti elettriche anche in piccola scala, senza la realizzazione di imponenti impianti industriali e soprattutto senza la produzione si scorie inquinanti. Sono nate così le prime celle solari
a effetto fotovoltaico.
Gli sviluppi hanno portato a diversi risultati e al giorno d'oggi l'energia fotovoltaica ha ormai fatto il suo ingresso nella vita quotidiana. Sia i favori delle industrie, sia l'interesse dei privati cittadini, contribuiscono a espandere questo tipo di ricerca, ottenendo numerosi successi nell'aumento
dell'efficienza di conversione energetica. Dal punto di vista della scienza dei materiali la prima cosa che viene in mente pensando alle celle
fotovoltaiche è il silicio. A tutti gli effetti la maggior parte delle celle sul commercio sono costituite da silicio policristallino, per le sue ottime qualità e proprietà di resa. Tuttavia esistono anche una moltitudine di altri composti, alcuni più recenti di altri, che sono ancora nell'occhio dei ricercatori, un esempio ne sono i recenti foto-materiali organici. Spesso però i costi di realizzazione sono alti per ottenere rese elevate, rendendo così proibitive le realizzazioni su impianti industriali. L'ossido rameoso (Cu2O) è stato uno dei capostipiti dei materiali utilizzati nelle celle fotovoltaiche.
Fin dal suo primo utilizzo nel 1958 esso ha presentato le caratteristiche di semiconduttore necessarie alla realizzazione di impianti fotovoltaici. Rispetto ai sui cugini più nobili, presenta delle efficienze minori, ma anche un costo decisamente più basso. Il rame infatti, da innumerevoli anni, è un elemento largamente sfruttato in tutti i campi dell'elettronica e non solo, e la realizzazione di ossidi specifici non comporta processi troppo complessi o costosi.
La ricerca nel campo dell'ossido rameoso è riuscita a migliorare le sue qualità all'interno del mondo fotovoltaico rendendo possibile la realizzazione di celle solari a costi contenuti.
Per questo motivo il Cu2O è tutt'oggi un materiale in grado di competere nel moderno panorama della ricerca solare fotovoltaica.
Tesi Bachelor Giovanni Vergari
Il plasma è un supporto particolarmente attivo dal punto di vista chimico e fisico. In base al modo con cui viene attivato e alla potenza di lavoro, può generare temperature basse o molto elevate e viene definito rispettivamente come plasma freddo o caldo. Quest’ampio range di temperature lo rende adatto a numerose applicazioni tecnologiche: rivestimento di superficie, smaltimento rifiuti, trattamento dei gas, sintesi chimiche, lavorazioni industriali. La maggior parte di queste applicazioni del plasma non sono ancora state industrializzate, sebbene il loro sfruttamento rispetti strettamente le norme sull’inquinamento.
I plasmi caldi (specialmente quelli ad arco) sono ampiamente industrializzati, con particolare diffusione all’interno del settore aereonautico. La tecnologia dei plasmi freddi è stata sviluppata in microelettronica, ma le apparecchiature da vuoto richieste ne limitano l’applicabilità.
Al fine di evitare l’inconveniente associato al vuoto, molti laboratori hanno provato a trasferire a pressione atmosferica processi che attualmente lavorano in vuoto. Le ricerche condotte hanno portato alla scoperta di varie ed innovative sorgenti che verranno descritte in questo elaborato.
Dopo un riassunto sui differenti tipi di plasmi, saranno descritte le varie sorgenti in termini di design, condizioni di lavoro e proprietà del plasma. In seguito l’attenzione sarà spostata sulle varie applicazioni (analisi spettroscopica, trattamento dei gas e processi sui materiali).
Tesi master Ram Khrishna Thakur
The lowest possible surface resistivity and higher accelerating field are the paramount
considerations, hence are obligatory for accelerating cavities. Since, superconducting materials
are used to make radio-frequency cavities for future accelerators. In the case of rf cavities,
superconductors are being used in order to minimize the power dissipated and increase the
figures of merit of a radio-frequency cavity, such as the quality factor and accelerating gradient.
Hence, these could be achieved by improving surface treatment to the cavity, and processing
techniques must be analyzed in order to optimize these figures of merit.
The research work reported in this dissertation mainly carried out on tesla type seamless 6GHz
Nb and Cu cavities. We have developed two innovative techniques: firstly, for mechanical
polishing of cavities, and secondly for purification of these cavities at atmospheric pressure under
cover of 4Helium gas (for protection) and at ultra-high vacuum (UHV) system. These cavities are
fabricated by spinning technology to create seamless cavities.
The main advantages of 6 GHz bulk-Nb cavities are saving cost, materials and time to collect
statistics of surface treatments and RF test in a very short time scale. Cavities are RF tested
before and after high temperature treatment under atmospheric pressure (under cover of inert gas
atmosphere to protect inner and outer surface of cavity) inside transparent quartz tube, and under
UHV conditions. Induction heating method is used to anneal the cavity at temperatures higher
than 2000°C and close to the melting point of Nb for less than a minute while few seconds at
maximum temperature. Before RF test and UHV annealing, the surface treatment processes like
tumbling, chemical, electro-chemical (such as BCP and EP), ultrasonic cleaning and high
pressure rinsing (HPR) have been employed. High temperature treatment for few minutes at
atmospheric pressure allow to reduce hydrogen, oxygen and other elemental impurities, which
effects on cavity Q-factor degradation, hence recovers rf performances of these cavities. This
research work will address these problems and illustrate the importance of surface treatments.
Tesi master Goulong yu
6 GHz spun seamless Superconducting Radio Frequency (SRF) cavities are a very
useful tool for testing alternative surface treatments in the fabrication of TESLA cavity.
However, the spinning technique has also some drawbacks like contamination, surface
damage in internal part due to the collapsible mandrel line. The first important step of
the surface treatments is the mechanical polishing. For this purpose, a new, cheap, easy
and highly efficient tumbling approach based on vibration was developed.
Before this approach was conceived, a few other methods, such as Turbula,
Centrifugal Barrel Polishing (CBP), custom Zigzag tumbler and “flower brush” have
been studied and tested. But the result was not so satisfactory neither for the low erosion
rate nor for the unstableness of the system nor for the complicated polishing process. At
last, a vibration system with a simple structure, working stably was created after two
experiments.
Another important task of the thesis is to update the optical inspection system for 6
GHz cavities. 3 stepper motors motor was added to move and rotate the cavity and
realized auto focus of the miniature camera. A software was developed to achieve a full
cavity photographed by one key operation using LabVIEW.
A high-efficiency mechanical polishing system is generally judged by two aspects:
one is whether the surface property satisfies the demand after polishing; the other is
whether the erosion rate can reach and be stabilized at a high value which is comparable
or greater than the existing products. The Radio Frequency (RF) test result indicates that
the vibration system is feasible. The latest erosion rate 1 gram/hour i.e. removing 13
microns depth of inner surface materials per hour exceeds the performance of CBP,
which is widely used in other laboratories in the world.
The mechanical polishing process is elaborated and cavities that have been polished
are listed. Several influencing factors on the erosion rate, such as tumbling time, media,
signal and multi-cavities and plate direction are discussed at the end.
A preliminary design of 1.3 GHz vibration system as the future development is
provided for the next plan.
Tesi magistrale Akaberi Nazkhatoon
In questo lavoro di tesi verrà presentato un primo prototipo di un mini inceneritore al plasma per la pirolisi dei rifiuti medicali basato sulla tecnologia delle torce al plasma a microonde (MW) con tecnologia domestica a basso costo.
Si inizia con una breve e generale descrizione sulle problematiche dei rifiuti, della loro classificazione e delle norme che ne regolano lo smaltimento. Quindi si parlerà delle norme necessarie per l‟identificazione dei rifiuti medicali ed infine verrà riassunta la modalità di gestione dei rifiuti secondo la normativa in vigore.
Successivamente saranno descritti alcuni metodi di termodistruzione dei rifiuti ospedalieri come la combustione negli inceneritori tradizionali, e alcuni metodi alternativi, come il trattamento al plasma atmosferico, andando ad analizzare vantaggi e svantaggi di ogni tecnologia.
L‟attenzione sarà quindi focalizzata sul plasma atmosferico e sulla descrizione delle sue proprietà. Quindi saranno descritti diversi tipi di plasma atmosferico in base alle condizioni operative di alimentazione e delle loro strutture concentrando le nostre attenzioni verso le torce al plasma atmosferico basate sulle microonde.
Quindi si descriverà la realizzazione di una torcia al plasma atmosferico utilizzando i componenti a basso costo dei normali forni a microonde e con l‟obbiettivo di utilizzare questa torcia sia nel settore industriale che nella ricerca.
Tale torcia, realizzata con componenti commerciali domestici a basso costo, costituirà il cuore del prototipo di mini inceneritore che è stato progettato, realizzato, descritto e testato in laboratorio. Verrà quindi illustrata l‟efficacia di trattamento di materiale rappresentativo di rifiuti medicali come: carta, cotone idrofilo e tessuti organici biologici.
Infine verranno descritte le linee guida per gli sviluppi futuri del prototipo al fine di aumentarne l‟efficienza nel trattamento dei rifiuti, nel recupero dell‟energia derivante dalla combustione dei syn-gas e nella purificazione dei gas da agenti inquinanti.
Tesi master Acosta Gabriela
This document provides a thermo-mechanical design of a high power neutron converter for the SPIRAL2 Facility. It includes 3 key parts:
1. A description of the neutron converter design including the graphite neutron converter, cooling system, delay window, beam collimator, and other components.
2. Analysis of material activation, radiation damage effects, and lifetime considerations for the graphite and other materials used.
3. Thermo-mechanical design calculations for the 50kW and 200kW neutron converters including temperature distributions, stresses, and deformations to validate the design meets specifications. Testing results of graphite evaporation rates, delay window performance, and ball bearing performance are also summarized.
Tesi PhD Zhang Yan
This document is the dissertation of Zhang Yan for the degree of Ph.D. It summarizes his research on sputtering niobium films into RF cavities and sputtering of superconducting V3Si films. The dissertation contains 6 chapters that discuss sputtering techniques for niobium cavities, sputtering niobium films on an RFQ model, co-sputtering and reactive sputtering of V3Si films, and thermal diffusion of V3Si films. The research aimed to develop sputtering methods for producing superconducting coatings on RF cavities and investigate the properties of V3Si films for potential use in superconducting radio frequency applications.
Tesi federico della ricca
Preparazione di un protocollo di deposizione magnetron sputtering di films sottili di Nitruro di Titanio
Tesi master Vanessa Rampazzo
Creazione di un database di attacchi chimici ed elettrochimici per il trattamento superficiale di metalli e leghe ad uso industriale
Tesi master Paolo Modanese
Il forno in alto vuoto della TAV è stato costruito per l’Istituto Nazionale di Fisica Nucleare agli inizi degli anni novanta ed è installato presso i Laboratori Nazionali di Legnaro (PD) nello stabilimento Alte Energie.
E’ stato realizzato in collaborazione con la ditta milanese TAV, che ha sede a Caravaggio (MI), specializzata nella produzione di forni in vuoto. E’ stato così possibile realizzare un forno mai costruito prima e che rispondeva appieno alle esigenze richieste.
Il forno in vuoto allora in uso era un modello a caricamento orizzontale le cui pareti interne e le resistenze erano realizzate in grafite. Da allora il vecchio forno è stato congedato, mentre il nuovo impianto è entrato subito in funzione per eseguire le brasature e i trattamenti termici sulle cavità acceleratici superconduttive a quarto d’onda dell’impianto Alpi.
Da allora fino ad oggi, il nuovo forno è sempre stato operativo, e grazie ad esso è stato possibile realizzare una grande varietà di trattamenti termici e brasature, per le più svariate applicazioni e impieghi.
Tesi Master Diego Tonini
La tecnologia degli acceleratori di particelle è tradizionalmente un serbatoio da cui attingere per il trasferimento di conoscenze tecniche dall’ambito della ricerca di base all’industria; in questo campo i Laboratori Nazionali de Legnaro dell’Istituto Nazionale di Fisica Nucleare (LNL – INFN) vantano una lunga esperienza come ente di ricerca di alto livello sia in ambito italiano che internazionale, nello sviluppo di nuove tecniche di accelerazione e nell’applicazione di conoscenze e metodologie tipiche della scienza dei materiali al campo degli acceleratori di particelle. Il master in Trattamenti di superficie applicati a tecnologie meccaniche innovative per l’industria si inserisce in questo contesto e funge da ponte per il trasferimento del bagaglio di conoscenze maturate durante gli anni per il trattamento dei materiali delle cavità acceleratrici a realtà industriali presenti sul territorio nazionale.
Il trattamento superficiale di una cavità acceleratrice superconduttiva è un passaggio fondamentale nella sua realizzazione, in quanto predispone lo strato superficiale del risonatore stesso a sostenere le condizioni di vuoto, temperatura ed alti campi elettrici presenti durante il funzionamento nell’acceleratore; questi trattamenti presuppongono un’approfondita conoscenza della scienza dei materiali ed una robusta preparazione di tipo applicativo oltre che teorico.
Il lavoro di questa tesi prende l’avvio da due istanze fondamentali, cioè
dall’applicazione delle conoscenze fisiche, chimiche e meccaniche apprese nel corso del master e dalla tradizione nello sviluppo di nuove tecniche di accelerazione dei Laboratori Nazionali di Legnaro con il fine di realizzare e caratterizzare un nuovo tipo di strutture acceleranti basate sul concetto di cristallo fotonico o photonic band gap (PBG) applicato alle microonde.
Durante questo lavoro si sono quindi realizzati alcuni prototipi di cavità PBG risuonanti a 14 e 6 GHz, in rame ed in niobio superconduttivo, sviluppando un metodo realizzativo che permettesse di evitare il ricorso a costose saldature electron beam; le cavità così realizzate sono state trattate superficialmente adattando il protocollo di trattamento utilizzato per altre cavità costruite nei Laboratori e studiando nuove strade tecniche per la loro finitura superficiale. Infine si è proceduto ad adattare i sistemi criogenici e RF
integrandoli per caratterizzare le cavità costruite.Questo progetto si inserisce in una collaborazione fra i Laboratori Nazionali di Legnaro
e la sezione INFN di Napoli, che ha fornito il supporto teorico sulla teoria dei cristalli fotonici applicati agli acceleratori e ha contribuito al progetto delle cavità attraverso le simulazioni dei campi elettromagnetici in cavità; il gruppo di legnaro si è occupato, oltre che della costruzione, dei trattamenti di superficie e delle misure, anche della parte riguardante la superconduttività in Radiofrequenza.
Tesi Master Giorgio Keppel
L’obiettivo di questo lavoro consiste nella progettazione e costruzione di un sistema UHV multicamera per la deposizione di film sottili. La tecnica
utilizzata per crescere i ricoprimenti sottili in questo caso è l’arco catodico continuo e pulsato. Questa tecnica permette di depositare film di elevato spessore in tempi estremamente veloci. La sorgente è pressoché puntiforme in confronto allo sputtering ed i film possono essere più spessi e più puri.
L’arc vapour deposition è una tecnica di deposizione di film sottiliche cade nella grande famiglia del PVD. Essa consiste nella vaporizzazione, da un elettrodo, del materiale che si vuole depositare per mezzo di un arco. La tecnica è veloce, efficiente e relativamente poco costosa: di conseguenza è uno dei metodi più usati a livello industriale per ottenere deposizioni di film sottili con ottime proprietà meccaniche.
Negli ultimi anni si stanno effettuando numerose ricerche, sia sperimentali sia
teoriche, al fine di mettere in evidenza come questa tecnica possa essere molto utile per produrre dei film sottili in grado di aumentare le proprietà fisiche e chimiche dei rivestimenti (come ad esempio un aumento della densità, un miglioramento dell’adesione al substrato, della stechiometria dei composti e di ulteriori caratteristiche chimico-fisiche).
In particolare la letteratura russa tratta numerosi esempi di come la tecnica
dell’arco, proprio grazie all’alto grado di ionizzazione dei vapori prodotti, renda possibile la produzione di rivestimenti con determinate proprietà chimico-fisiche e strutturali per particolari condizioni di processo, non altrimenti ottenibili con altre tecniche competitive quali il magnetron sputtering o l’evaporazione tramite electron beam Come si vedrà in
seguito, infatti, l’arc vapour deposition ha il grandissimo vantaggio di controllare non solo la ionizzazione degli atomi che si vogliono depositare, attraverso una combinazione di campi elettrici e magnetici, ma anche l’energia con la quale gli ioni arrivano sul substrato.
Le sorgenti ad arco vengono inoltre utilizzate come sorgenti per LRQ EHDP che
devono produrre elevate densità di corrente.
Nel mondo industriale, infatti, questa tecnica riscuote molto interesse.Il deposito tramite arco catodico è un processo fisico sottovuoto che consente la
crescita di film duri, compatti ed aderenti su un ampio spettro di materiali al di sotto dei 300°C: Il film, estremamente sottile, ha durezze da 1000 a 3500 HV: le applicazioni industriali sono molte e variano dalla ricopertura di utensili da taglio agli tampi per le materie plastiche e lavorazioni meccaniche, da prodotti d’arredamento (maniglie, copri interruttori, pomoli, etc.) a componentistica da bagno (rubinetti, docce, tubi, etc.).
......
Tes master Tommaso Cavallin
Fu una scoperta sensazionale quando Jun Akimitsu e colleghi annunciarono la loro scoperta nel gennaio 2001 che il diboruro di magnesio diveniva superconduttore attorno ai 40 K. L’interesse degli autori era inizialmente rivolto verso il semiconduttore CaB6 , il quale diviene ferromagnetico a seguito di trattamento leggero di doping. La loro intenzione era quella di sostituire parzialmente degli atomi di carbonio con altri di magnesio, omologo come shells elettronici ma più leggero, e gli parve conveniente utilizzare il diboruro di magnesio (ben noto sin dal 1953) per questo scopo.
L’aspetto interessante è che il magnesio diboruro è un composto molto usato nelle reazioni di sintesi del boro, dei borani, o di bururi di metalli di transizione e facilmente reperibile in qualsiasi laboratorio di chimica. E’ dunque facile immaginarsi lo stupore del mondo scientifico quando fu
comunicato che il MgB2 diviene superconduttore a temperature mai raggiunte sino ad allora da sistemi basati su semplici leghe intermetalliche non ossidate. Le fievoli speranze ed il derivante
mitigato interesse che vi era attorno ai superconduttori all’inizio della seconda metà del 1900 era dovuto soprattutto a due figure ....
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Our observation is that multiple layers — hardware, operating systems, third-party libraries, software versions, input data, compile-time options, and parameters — are subject to variability that exacerbates frictions but is also essential for achieving robust, generalizable results and fostering innovation. I will first review the literature, providing evidence of how the complex variability interactions across these layers affect qualitative and quantitative software properties, thereby complicating the reproduction and replication of scientific studies in various fields.
I will then present some software engineering and AI techniques that can support the strategic exploration of variability spaces. These include the use of abstractions and models (e.g., feature models), sampling strategies (e.g., uniform, random), cost-effective measurements (e.g., incremental build of software configurations), and dimensionality reduction methods (e.g., transfer learning, feature selection, software debloating).
I will finally argue that deep variability is both the problem and solution of frictionless reproducibility, calling the software science community to develop new methods and tools to manage variability and foster reproducibility in software systems.
Exposé invité Journées Nationales du GDR GPL 2024
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Conducted over a period of >200 years, Thermodynamics R&D, and application, benefitted from the highest levels of professionalism, collaboration, and technical thoroughness. New layers of application, methodology, and practice were made possible by the progressive advance of technology. In turn, this has seen measurement and modelling accuracy continually improved at a micro and macro level.
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- 1. Secondary Electron Yield for SRF Materials Sarah Aull
- 2. Looking back to the SRF13 • 500 nm MgB2 on a Nb substrate (deposited by Chris Yung at STI) • Strong multipacting on 1st RF test • After new rinsing: even stronger multipacting + „burn marks“ in high E field regions • XPS measurements show only 70% MgB2 Cause for multipacting? Emax sarah.aull@cern.ch 2
- 3. Secondary Electron Yield (SEY) • SEY = # 푠푒푐표푛푑푎푟푦 푒푙푒푐푡푟표푛푠 푝푟푖푚푎푟푦 푒푙푒푐푡푟표푛 • Primary electron travels through the material, creating secondaries • Most secondaries are produced at the end of the primary path • Penetration depth 푅푚푎푥~퐸0 primary energy • Probability of emission decreases exponentially with depth XS • 푅푚푎푥 ≪ 푋푆: Few secondaries, but easy emission • 푅푚푎푥 ≫ 푋푆: Many secondaries, but low emission sarah.aull@cern.ch 3
- 4. SEY of (non) conductors • SEY is closely connected to the electrical conductivity • Metals: • internal secondaries scatter mainly with free electrons • Vacuum barrier is in the order of 10 eV • low SEY: 0.5 (Li) – 1.8 (Pt); SEY(Nb) = 1.3 • Insulators: • Internal secondaries scatter with phonons and defects • Vacuum barrier is in the order of 1 eV • High SEY: 4 – 15 (MgO) • The SEY of alloys ranges usually between 1.5 and 3 Literature values usually refer to pure material, not the technical surfaces! sarah.aull@cern.ch 4
- 5. Influence of the Surface • If the primary electron arrives in a grazing angle, secondaries are more likely emitted ( higher SEY) • If the surface is rough, emitted secondaries can be reabsorbed ( lower SEY) • Oxides and contamination on the surface might influence the SEY significantly • Contamination: hydrocarbons, condensed water and gases (especially on a cryogenic surface), foreign material sarah.aull@cern.ch 5
- 6. SEY setup at CERN • SEY measurement • under UHV • at room temperature • with normal angle • SEY = 퐼collector 퐼sample+퐼collector • Sample can be transferred to the XPS setup under vacuum so that the surface condition is not altered. sarah.aull@cern.ch 6
- 7. • The XPS setup includes a sputter ion gun (Argon) • XPS measurements were performed with every SEY measurement (before and after sputtering) to estimate the cleanliness of the surface • Sputtering removes contaminants but also changes the chemical composition of the surface! • Few nm were sputtered off for removal of the carbon peak sarah.aull@cern.ch 7 XPS & Sputtering Nb
- 8. From SEY data to multipacting in a cavity • Gases will condense on the cold surface • RF conditioning will not remove nm of material, but helium processing might • Angular dependence might play an important role • It is unknown if the SEY changes below Tc The SEY data before and after sputtering serves as a bad case and good case scenario! sarah.aull@cern.ch 8
- 9. SEY of technical bulk Nb • Both samples cut from same Nb sheet. • Carbon and oxides have strong impact on the SEY. sarah.aull@cern.ch 9 47 5 38 10 23 7 57 13 32 18 45 47 43 5 5 4 60 50 40 30 20 10 0 C Nb O Rest Atomic Composition [%] BCP BCP degreased EP degreased EP sputtered
- 10. NbTiN • Kindly prepared by A-M Valente-Feliciano, JLab • NbTiN on Nb via HIPIMS sarah.aull@cern.ch 10 33 9 2 11 41 35 5 3 0 29 23 9 50 40 30 20 10 0 C 1s N 1s Na 1s Nb 3d5 O 1s Ti 2p3 Atomic Composition [%] before sputtering after sputtering
- 11. Nb3Sn • Kindly prepared by Sam Posen, Cornell • Nb3Sn on Nb via reactive evaporation • Nb3Sn cavity did not reach multipacting band yet sarah.aull@cern.ch 11 26 48 8 2 15 5 55 26 1 13 60 50 40 30 20 10 0 C 1s O 1s Nb 3d5 Cu 2p Sn 3d5 Atomic Composition [%] before sputtering after sputtering
- 12. MgB2 • Kindly provided by X.X. Xi, Temple University • No sputtering to avoid further oxidation • Formation of MgO will increase the SEY. sarah.aull@cern.ch 12 18 21 1 1 16 43 17 25 2 0 15 41 50 40 30 20 10 0 B 1s C 1s Cl 2p3 F 1s Mg 2s O 1s Atomic Composition [%] 1018c 1018d
- 13. Conclusion • The SEY of technical surfaces need to be considered for SRF applications. • SEY of NbTiN & Nb3Sn comparable to Nb (after sputtering). • Validation through RF tests is however needed. • MgB2 needs a non-dissipating passivation with low SEY. sarah.aull@cern.ch 13
- 14. Acknowledgements • Thank you for providing and preparing samples: • MgB2 for the QPR: Chris Yung, STI • MgB2 for SEY: Xiaoxing Xi, Temple University • NbTiN; Anne-Marie Valente-Feliciano, Jefferson Lab • Nb3Sn: Sam Posen, Cornell • Nb: Nuria Valverde Alonso, CERN • BCP/EP: Serge Forel & Leonel Ferreira, CERN • Mauro Taborelli for access to the SEY setup • Mounir Mensi and Holger Neupert for performing the measurements with me (and answering all my questions). sarah.aull@cern.ch 14