wg-1 summary · arely cano - new insights on the srf nb cavities performance from spectroscopic...
Post on 24-Sep-2020
1 Views
Preview:
TRANSCRIPT
WG-1 SummaryKensei Umemori, Ari Palczewski, Marc Wenskat
TTCWorkshop@CERN2020
Teaser:
Highly subjective summary – put together in short amount of time – sorry if I missed
something you found important – all mistakes or unclear slides are my fault
• We have a set of approved methodes to make a cavity work
• We accepted hypotheses on why they work and moved on to
production
• We start to look at those methodes again – in the light of new
discoveries/recipes but also we simply want to understand
• Material/surface physics + state-of-the-art techniques become
more and more important
Some Facts
• 4 Sessions (3 on Tuesday, 1 on Wednesday)
o R&D involving Cavities (1Session)
o R&D involving Samples (2Session)
o R&D regarding flux trapping (1Session)
o Of course some overlap
• 19 Speaker
o 15m/4w
o America:10 Asia:3 Europe: 6
• 1 Sample Survey
o Was sent to labs prior the workshop
o Try to compare intention/material/preparation/handling/analysis
Kensei Umemori - New results of KEK infusion and mid-T bake
Sam Posen - The In-Situ Mid-T Bake
Infusion-like N profile
Lea Steder - Recent SRF cavity treatment R&D @ DESY
Chao Dong - High Q&G activity at IHEP• Many activities
o Vacuum furnaces for doping and Nb3Sn
o New Tuning Machine
o Optical inspection cameras
o CBP
o TX-Mapping & 2nd Sound
Only BCP!
David Longuevergne - Status of infusion studies at IJCLab/IRFU
• New Furnace purchased
• Commissioning studies showed a nice,
clean furnace
• First cavities outgassed looked good
• First 150°C infusion run failed
• Cleanliness of N is investigated
Pashupati Dhakal - Status of Infusion Studies at Jlab
• Restart R&D after furnace upgrade
• Systematic study on
o Actual cavity T
o Injection T
o Frequency dependence
• fvsT data used to track changes in
ζ/ℓ
Daniel Bafia – Progress in N-Doping at FNAL – New Higher Gradient Insights
• Investigated T-map for different quench patterns or N-doped cavities.
• Higher quench fields quenched closer to the equator with a mechanism that is likely of magnetic origin
• Lowest quench field (18MV/m) quenched near the iris and is likely due to the heating of a nitride
M. Checchin - LCLS-II investigation of failed LCLS-II HE prototype cavities EP analysis
o Final EP temperature is the principal parameter controlling the maximum accelerating gradient in N-doped cavities
o The colder the EP the higher the maximum gradient achievable
o Cold EP (< 16 C) is most likely allowing for an etch-free EP process and a smoother surface
Phillipp Kolb - Test Results from the TRIUMF Multi-Mode Coaxial Resonators
𝑅𝑆 (𝐵, 𝑇) =𝐴 𝐵𝑝, 𝜔
𝑇exp −
𝐶 𝐵𝑝, 𝜔
𝑇+ 𝑅𝑇𝑖(𝐵𝑝, 𝜔)
R vs B data
collected from
QWR and HWR
for wide range of
frequency from
200 ~ 1200 MHz
Attempted
N-infusion
for QWR
Flux expulsion for QWR
Alexander Romanenko - Oxygen role in the high field Q-slope / mild baking –revealed by TOF-SIMS + cavity surface engineering studies
Oxygen diffusion at 120C Oxygen diffusion at
205C
200C, 1h works just as well
as 120C, 48h for HFQS
elimination
BCS & residuals for 120 –
200 C BCS & residuals for 400 –
500 C
Effect of oxygen diffusion during baking process was investigated.
Baking
temperature and
duration time
change cavity
performance,
R_BCS, Rres,
quench field etc.
Small sample survey – Tuesday afternoon
• Thank you very much for your cooperation.
• Still welcome survey data from missing Labs.
Embedded survey data in
the file link below. Click to
open in Excel
Palczewski/Umemori/Wenskat WG1 Review 15
Anton Ivanov - Flux Expulsion Measurement with Flux Lens
Palczewski/Umemori/Wenskat WG1 Review 16
• Some deformation structures could
persist even after 900°C, 950°C...
Strength of the structure and
mechanical stability needs to be
considered while increasing heat
treatment temperature.
• Upstream processing activities need
attention for future high-Q high-G
cavities.
• We are working on establishing vendor
relationships to create variations in Nb
sheet material.
Shreyas Balachandran - Microstructure correlations and flux-trapping in SRF
Nb- Role of initial microstructures
Palczewski/Umemori/Wenskat WG1 Review 17
• Possible pinning change from nitrogen doping, but questions about heat treatments
• Strong pinning tested in Nbti cavities, could be used in high magnetic field environments
Hai-Hu Wen - Vortex penetration and dynamics of Nb, N-doped Nb and NbTi
plates
Palczewski/Umemori/Wenskat WG1 Review 18
• We see a trend at 900C that correlated grain size and measured flux expulsion
• Still need to verify if this is a “Possible method for sorting material at Nb vendor”
Paulina Kulyavtsev - Flux expulsion on small samples for LCLS-II HE
Márton Major - Material studies on High-T Doping
Palczewski/Umemori/Wenskat WG1 Review 19
Original 1983 in
Wuppertal by G. Müller
• Using XDR to evaluate the growth of d-NbN vs growth parameters
• Similar to Nitrogen doping, but at much higher temperatures, cavity soon
Arely Cano - New insights on the SRF Nb cavities performance from
spectroscopic data
Palczewski/Umemori/Wenskat WG1 Review 20
• Hydride suppression see through
Raman spectroscopy • Possible shift Nb 3d spectral seen
though XPS depth profiling
• Rough surface of cavity cutouts post EP
Dirk Lützenkirchen-Hecht - In-situ EXAFS investigation of N2 - treatment of Nb
Palczewski/Umemori/Wenskat WG1 Review 21
• N2 -uptake in Nb on interstitial octahedral sites, increasing with time and pressure
• In- and ex-situ measurements agree with each other
• precision measurements foster trends (slightly increased average Nb-Nb-distance &
disorder)
Jonathan W. Angle - Challenges of SIMS Calibration for N-Doped Niobium
Palczewski/Umemori/Wenskat WG1 Review 22
• Even with RSF difference, good reproducibility can be achieved with a quality surface
and a good tune.
• Implant standard becoming more simple - to systematically evaluate the different
parameters
• Path to fully calibrated SIMS measurements is becoming clear
Marc Wenskat - Sample Studies on Nitrogen- and Heat-Treatments of Niobium
Palczewski/Umemori/Wenskat WG1 Review 23
• Broad spectrum of sample R&D results shown Nb2C contamination, near-surface vacancy-
clusters and flux trapping in quench spot. A NbN phase forming during 120°C.
• All results tend to say: Do not bring H into Nb (e.g. cold EP) but if it is there, try to
distribute it controlled (v+nH) or trap it (O, N) to prevent formation of Nb-hydrides.
top related