383 – The LHC Beam Dump
Gast: Marco Calviani Host: Markus Völter Shownoter: Kolja Dummann
The beam dump is a large graphite block used to take up the energy stored in the LHC beam in case the beam needs to be shut down. Since the energy in the beam can be as high as the kinetic energy of a landing 747-400, designing and operating the dump is challenging. In this episode, Marco Calviani, who heads the group that is responsible for this and other beam dumps at CERN, tells us about how the dump works, and what they have recently changed in order to cope with the higher luminosity in future configurations of the LHC.
Faster-than-light neutrino anomaly | CERN Neutrinos to Gran Sasso | Simon van der Meer | Fermilab | Graphite (omega tau 344 – History and Development of ATLAS) | Compact Muon Solenoid
The LHC Beam Dump00:16:09
(Beam Intercepting Devices at CERN – Types, Challenges, Design, R&D and Operation (1/2) | Beam Intercepting Devices at CERN – Types, Challenges, Design, R&D and Operation (2/2)) | Proton Synchrotron Booster (PSB) | High-Luminosity LHC
(omgea tau 096 – Controlling the LHC Beam) | LHC Abort Gap Monitoring and Cleaning (Chapter 17 - Beam Dumping System)
Enhancing the Beam Dump00:51:29
The SPS & PS Dump01:06:54
FCC Beam Dump01:17:00
Wo sind denn die Links zur Folge am Ende? Bei den letzten paar Folgen sind sie anscheinend auch verschwunden.
»Gast: Markus Völter Host: Marco Calviani«
/me confused …
And I have allready an idea how to solve Marco’s cooling challenge of the beam dump – with water, but without any mechanical connections …
Bitte den Feed neu abonnieren. Die /feed URL tut nicht mehr.
Oops, fixed, danke :-)
Dear Markus and Marco,
Thanks for this interesting episode. I have questions about one detail that was not discussed. The window between the vacuum tunnel and the beam dump. How is it built? What does the beam do to it when passing? Anything else that is interesting about it?
Marco, you said that the force on the dump was not connected to the conservation of impulse. If not, what happens to the impulse?
It would be fantastic if you could poste a quick answer.
Thanks and best regards,
@Werner – thanks a lot – nice to read form you.
Looking forward to any comments and suggestions you may have ;).
@Volker, thanks for your comment indeed.
Concerning the first question: the window that separates the UHV part of the machine from the air/nitrogen is currently made out of 15 mm thick CfC disk coupled with a 250 um 316L foil. The first one guarantees the mechanical stability under the mechanical load imposed by the vacuum while the second guarantees the vacuum tightness. The dump windows are now made by TiGr5 disks 10 mm thick as we demonstrated a more robust design with these.
Concerning your second question: the relativistic momentum of 7 TeV protons (even when considering the full machine at relatively high intensity) is still relatively low with respect to the mass of the dump itself. So indeed, the transfer occurs, but it is low as to be almost negligible. However the energy of the beam is huge and generated significant temperature increase in a very short time, resulting in large dynamical effects. Hope this clarifies.
Thanks a lot for your answer!
CfC = carbon fiber carbon composite? Covered by a (316L) steel foil? And the beam simply passes through them without damage? Wow, I hope to understand sometime what gets damaged by the beam and what not. Maybe one day you can put a slice of meet in front of the dump to answer the question, what would happen to your hand if you put it into the beam. Might result in a fun paper ;-)
Thanks for your answer about the momentum. For some reason I had in the back of my mind comparisons to trains or air planes. But now I found that the kinetic energy is “only” that of a motorbike (https://www.lhc-closer.es/taking_a_closer_look_at_lhc/0.energy). But with LHC Run 3 that should change. If I googled correctly than the kinetic energy will increase from 0.13 MJ to 560 MJ, a factor of 4300. If I calculated correctly that would be the energy of a 460 ton train (German ICE 3) at 175 km/h. Good luck with your next beam dump!
Indeed the window that separates the vacuum from the air of the dump cavern is constituted by 15 mm carbon fiber composite followed by 250 micrometer stainless steel foil. The foil guarantees the vacuum tightness, while the CfC disk provides the mechanical stability (on the contrary, the windows that contains the dump core are 10 mm thick titanium grade 5). The proton beam releases very little energy in such a low density material (CfC) or given the very thin layer of stainless steel (where energy is lost mainly by ionisation losses). The beam matter interactions and coupled mechanical stresses – generated by the asymmetric energy deposition – is quite a complex subject indeed, but there are clear patterns.
For the energy/momentum: the link you provided is correct, but the calculations take into an account a single bunch. Indeed when you dump the full beam you have roughly 2700 bunches… So you would have to consider the kinetic energy of 2700 motorcycles, depositing their energy all of a sudden in 90 microseconds. For the total energy, we will pass from 320 MJ of Run2 (end of 2018) to 540 MJ in Run3. 700 MJ will be reached in the HL-LHC era (2029 onwards) (more details here: http://dx.doi.org/10.1088/1748-0221/16/11/P11019 ).
Let me know if you need further clarifications.
Great! Thanks, Marco! I saw your answer just now.