Transcript Document 7342395

Irradiation Damage in LHC Beam
Collimating Materials
N. Simos (BNL) & N. Mokhov (FNAL)
LARP Collaboration Meeting
SLAC
October 17-19, 2007
Proposal - LHC Material Studies
LHC Collimator Material Irradiation Damage Studies – to date
•
•
•
•
•
•
•
Carbon composites (including the 2-D carbon used in Phase I) exhibit stability
in their thermal expansion coefficient in the temperature range they are
expected to operate normally during PHASE I.
Carbon composites experience dramatic change in their CTE with increased
radiation BUT are able to fully reverse the “damage” with thermal annealing
Carbon composites also showed that with increased proton fluence (> 0.2
10^21 p/cm2) they experience serious structural degradation. This finding
was confirmed for the family of such composites and not only for the 2-D
composite used in the LHC (recent data on P-bar target at FNAL confirm the
findings of this study)
Thermal conductivity loss measured after irradiation is a serious problem for
these composites
Also experimentally shown, and under similar conditions, graphite also suffers
structurally the same way as the carbon composites (also experiences serious
thermal conductivity loss)
Proton radiation was shown to not effect the thermal expansion of Copper
and Glidcop that are considered for Phase II. Reduction in thermal
conductivity is observed but not anywhere near what carbon and graphite
sees. Still an issue for Glidcop (this is primarily the effect of alloying copper
with aluminum)
Encouraging results were obtained for super-Invar, Ti-6Al-4V alloy and
Proposal - LHC Material Studies
AlBeMe
LHC Collimator Material Irradiation Damage Studies – to date
• Study results have provided key information
on the choices made thus far in collimating
the LHC beam and on where should one looks
(or avoid looking altogether as power is
increased).
• The proceedings of the recent Materials
Workshop and the needs identified, form the
basis (along with the findings of the study
thus far) of what to do next.
Proposal - LHC Material Studies
LHC Collimator Material Identified Needs
Reaching nominal power and planned upgrades
• Pool of common materials (including Phase I and II choices)
unable to get the machine to the next level
• While design schemes can get more clever, still the limitations
are dictated by materials
• Identified new materials and composites (diamond-metal
composites, carbides, etc.) have no track record and therefore
irradiation studies are needed
• As power of the machine increases, gamma and neutron fluxes
downstream of the collimation space becomes more of an issue.
Studies attending to the effects on materials induced by the
gamma/neutron cocktail are a wise step forward
• As power increases, shock-induced damage to collimator from a
full beam is an issue. For current matrix of materials and for new
pool under consideration, response under such high-strain rate is
unknown
• High-strain rate (shock) on collimator materials in un-irradiated
state is one thing, BUT shock on irradiated materials is a
different ball game. Proposal - LHC Material Studies
Collimator and Absorber Materials Workshop
Proposal - LHC Material Studies
LHC Collimator Material Identified Needs
Workshop Summary (1)
Interesting new materials include Diamond-Metal Composites, CarbonNanoFiber/Cu,
etc.
• Not a single solution for all applications and problems can be found
• A material matrix to be prepared to point out strengths and weaknesses of each
material and availability in time
• A similar matrix should be prepared for different protection devices and
requirement in time
• Collaboration to be launched for mechanical tests to be followed by irradiation
studies
• Reconsider surface coating to improve RF behavior
• Carefully consider material vs. vacuum behavior
• Qualify materials at high strain rates (change of physical properties with strain rate)
• Better qualify anisotropic material
• Should we go beyond the continuum material assumption?
• Material optimization must go with design optimization (an idea for next
workshop?)
Proposal - LHC Material Studies
Proposal - LHC Material Studies
7
LHC Collimator Material Identified Needs
Workshop Summary (2)
Experimental results and future tests:
• •
Techniques to detect beam accidents that might have damaged collimators /
beam absorbers; the efficiency of the detection methods need still to be
demonstrated.
• •
Material characterization, static and dynamic (parameters might change
during shock impact)
• Radiation issues and irradiation tests:
– •
– •
– •
great interest of several labs, possibly also for ITER
further tests at BNL and at Kurchatov Institute are planned
there are other accelerators where tests could be done (Fermilab, Los
Alamos, CERN, ……)
– •
there are several factors to radiation damage such as particle spectra,
time scale of irradiation and dose rate
– •
concrete plans with time schedules are required, who does what?
– •
observations of past accidents should be simulated with codes
Proposal - LHC Material Studies
REQUEST TO LARP
To further investigate materials already identified as
promising as well as new exotic composites for LHC-like
irradiation conditions - particles, energy spectra and
temporal - initiate a task “LHC Materials Studies”.
This would be a continuation of the previous LARP task,
utilizing the unique BNL set-up and expertise. Deliverables
would also include an integrated software package for
reliable prediction of radiation effects, benchmarked in
dedicated measurements. The list can be extended to
materials used in superconducting magnets and a crystal
collimation setup.
Estimated load is 0.2FTE + $200k/yr for 3 years.
Interested parties: BNL, FNAL, SLAC, CERN, PSI & GSI
Proposal - LHC Material Studies
Plan for LHC Materials Studies
1. Damage assessment of materials that thus far exhibited good
behavior (AlBeMet, Ti-alloy and super-Invar) under higher
fluences than those achieved to-date
2. Irradiation damage of new and exotic composites (under
discussion at CERN) that may get LHC to both nominal and
upgraded power (diamond-metal composites, nano-structured
materials, etc.)
3. Neutron/gamma irradiation studies (see next 3 slides)
4. Shock (high-strain rate) effects on irradiated materials. Highpower laser based studies utilizing the BNL set-up in the hot
area where irradiated materials are studied
5. Numerical simulation study of damage under normal and shock
operations by interfacing MARS code with non-linear structural
analysis codes exploring shock-induced behavior. Use laser
induced shock to benchmark such a numerical approach
Proposal - LHC Material Studies
Neutron/Gamma Irradiation at BNL
112-MeV protons
Proposal - LHC Material Studies
At 1012 p/s
Neutron/Gamma Irradiation at BNL
At 1012 p/s
Proposal - LHC Material Studies
Protons, neutrons, photons and
electrons in Invar
•
At 1012 p/s
<E> (MeV) Flux (cm-2 s-1)
p: 23
8.6e5
n: 9
1.9e9
g: 1
3.2e9
e: 1
7.1e6
Here protons include those
from neutron-induced
reactions (recoils etc)
Contributions to absorbed
dose are not very different!
Proposal - LHC Material Studies
Summary of Results of Interest
(to-date)
Proposal - LHC Material Studies
Collimation Irradiation Damage Studies
PRIMARY
•
•
•
Carbon Composites (2-D and 3-D structure)
Copper (annealed)
Glidcop_15AL – Cu alloyed with .15% Al (axial cut and transverse cut)
SECONDARY
•
•
•
Super-Invar
Toyota “Gum Metal”
Graphite (IG-430 “isotropic”)
ALSO candidates under consideration
•
•
•
•
Ti Alloy (6Al-4V)
Tungsten
Tantalum
Low-Z alloy - AlBeMet
Proposal - LHC Material Studies
Annealing behavior also exhibited by 2D Carbon !
(fluence ~ 10^20 protons/cm2)
Weak direction (orientation normal to fibers)
Fiber (strong) direction
Proposal - LHC Material Studies
A threshold exists on carbon composites and graphite (fluence ~10^21 p/cm2)
P-bar Target Experience (when enclosed in CC composite damage was seen with similar fluences)
2-D carbon
3-D carbon
Proposal - LHC Material Studies
graphite
Irradiation Effects on Copper
(fluence ~ 10^21 protons/cm2)
Proposal - LHC Material Studies
Irradiation Effects on Glidcop
(fluence ~ 10^21 protons/cm2)
Proposal - LHC Material Studies
Irradiation studies on super-Invar
“invar” effect found in Fe-Ni alloys  low CTE
– “inflection” point at around 150 C
Effect of modest irradiation
Annealing or defect mobility at elevated temperature
Proposal - LHC Material Studies
“annealing” of super-Invar
Following 1st irradiation
Following annealing and 2nd irradiation
ONGOING 3rd irradiation phase: neutron
exposure
Proposal - LHC Material Studies
Radiation Damage Studies – Other Candidates
Proposal - LHC Material Studies
Radiation Effects on Conductivity
Proposal - LHC Material Studies
Electrical resistivity  Thermal conductivity
Proposal - LHC Material Studies
Some VERY preliminary results
Glidcop in both axial and transverse directions (~ 1 dpa)
sees 40% reduction
3-D CC (~ 0.2 dpa) conductivity reduces by a factor of 3.2
2-D CC (~0.2 dpa) measured under irradiated conditions
(to be compared with company data)
Graphite (~0.2 dpa) conductivity reduces by a factor of 6
Proposal - LHC Material Studies