MUFO?

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KropotkinPete
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MUFO?

Post by KropotkinPete » Sat Apr 18, 2015 1:15 pm

What is a MUFO? A microUFO? I can't find MUFO or UFO in the acronym list.

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Tau 2
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Re: MUFO?

Post by Tau 2 » Sat Apr 18, 2015 3:19 pm

KropotkinPete wrote:What is a MUFO? A microUFO? I can't find MUFO or UFO in the acronym list.
Quite the contrary, It is a Mega UFO. The first mention of it was in the morning meeting on Tuesday 14 March:
In the morning meeting, they wrote:Comparison to UFO-Model
Preliminary analysis indicates that the particle needs to be very large:
150 µm radius. (Pre-LS1 UFOs were modeled with radii <50 µm.)
Due to the small intensity it falls through the center of the beam, hence the large
loss rate and long loss duration.
Later, I saw the term "Mega UFO" or MUFO appear.
They seem only to appear on one location (called B15R8, near point 8), so there is probably some source of particles in there somewhere. They already deployed some portable BLMs (Beam Loss Monitor, a detector of particles) to locate it more precisely.
This morning, they heated up (that is, made it less cold, to 78K) the beam screen (i.e. wall of the tube), in order to see if that makes a difference. Also, they steered the beam to very near the wall for a while (they call that a bump).
Next step is to do this during a ramp. We'll see what comes out...
- Tau

KropotkinPete
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Re: MUFO?

Post by KropotkinPete » Sat Apr 18, 2015 3:51 pm

Thanks for the info!

josch222
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Re: MUFO?

Post by josch222 » Mon Apr 20, 2015 10:44 am

In the slides from the morning meetings they call it multiple UFOs because they have the strange
behavior of creating a pattern of multiple loss spikes.
It can be seen on page 18 of the minutes from today, in earlier ones too:
https://indico.cern.ch/event/385865/con ... des/0.pptx

In an earlier minutes it was written they have no model for this, I'm not sure if it was meant to have
no simulation model for this or that they have simply no idea what causes the pattern.

My suggestion is: Its a very light particle, not falling through the beam but being deflected upwards
(and in beam direction) and falling back multiple times. May be mites having fun surfing on the beam :D

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Tau 2
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Re: MUFO?

Post by Tau 2 » Mon Apr 20, 2015 5:16 pm

Well, the good news is that is seems to be gone.
It might be that heating the beam screen solved the problem: it hasn't been seen since, even though they sent the beam right next to the probable source, as far left, right, down and up (in that order) as they could: no more MUFOs.
But it also might be luck. It seems that there is something in the low part of the tube (could be laying debris that caused the MUFOs in the first place, who knows?).
I'll keep you posted if more news comes.
- Tau

josch222
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Re: MUFO?

Post by josch222 » Tue Apr 21, 2015 4:46 am

They suspected frozen gas, that could explain that its gone after heating.
Would it be possible that the proton beam attracts flakes of it due to electrostatic force?
If so, it would provide a scenario for a bouncing particle: Neutral particle attracted by positive charge,
after contact it is charged and moves to the beam screen where it discharges.
Repeat until it is gone or sticks to the pipe.
Because there are other forces than only gravity it may be possible that it stays longer in the beam
and looks bigger than it is.

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Re: MUFO?

Post by josch222 » Tue Apr 21, 2015 9:23 am

There are news, it looks like there is a big object in the lower part of the beam pipe:
Page 12
https://indico.cern.ch/event/385865/con ... ides/0.pdf

My guess: Its an M8 or M10 nut or bolt ;-)

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Tau 2
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Re: MUFO?

Post by Tau 2 » Tue Apr 21, 2015 10:16 am

I just read that they named it, in their typical CERN way, an ULO (Unidentified Laying Object). :lol:
- Tau

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Tau 2
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Re: MUFO?

Post by Tau 2 » Wed Apr 22, 2015 4:38 pm

The latest news is that they tried to scrape the ULO with a "nominal" beam, that is a single bunch of about 100 billion protons in this case.
This resulted in the ULO being 1 mm lower, so it is now 6 mm under the center of the tube. This might be enough.
:shifty:

What happened the last few days is mainly preparation for more serious ("nominal") beams:
  • The ADT has been set up (to nudge individual bunches that are misbehaving
  • Injection and dump kicker magnets are accurately timed
  • The abort gap keeper is set up (that makes sure there is enough empty space between the bunches for the dump kicker to fire
  • further calibration of the BPMs
  • even some adjustments to the SPS
  • further setting up of the protection mechanisms (more protons=more danger, of course)
  • setting up the BCT and FBCT to accurately measure the higher number of protons (there still are glitches, but this wil be fixed soon)
Current news: they are now busy setting up the orbit for different circumstances:
  • with or without crossing angle for the experiments
  • with or without experiment magnets
  • during the ramp
So you can expect more intensity the next few days! :geek:
They just did a ramp to 6.5 TeV of intensity about 14 billion protons, which is equivalent to 15 kJ (about the kinetic energy car going 20 km/h. Not much yet, but it can still cause real damage).
- Tau

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chelle
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Re: MUFO?

Post by chelle » Wed Apr 22, 2015 6:00 pm

Tau 2 wrote: ULO (Unidentified Laying Object).
It's 'Lying' without an a :dance:
Dance, even if you have nowhere to do it but your own living room.
Wear Sunscreen by Baz Luhrmann - Mary Schmich

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Tau 2
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Re: MUFO?

Post by Tau 2 » Wed Apr 22, 2015 6:55 pm

chelle wrote:It's 'Lying' without an a :dance:
I thought that meant "not speaking the truth".
Wonder how you spell that, then.
- Tau

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chelle
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Re: MUFO?

Post by chelle » Wed Apr 22, 2015 7:33 pm

Tau 2 wrote:
chelle wrote:It's 'Lying' without an a
I thought that meant "not speaking the truth".
Wonder how you spell that, then.
"Not speaking the truth" is the same.

Lay is also the past of Lie.

The differences are subtle almost similar like in Dutch: Liggen (lie) vs. Liegen (lie) vs. Leggen (lay)
Dance, even if you have nowhere to do it but your own living room.
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Re: MUFO?

Post by dukwon » Thu Apr 23, 2015 6:42 am

"Lay" is something you do to an object, "lie" is something a subject does to itself. You can lay down a carpet and lie down on it afterwards.

josch222
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Re: MUFO?

Post by josch222 » Thu Apr 23, 2015 8:21 am

Tau 2 wrote:The latest news is that they tried to scrape the ULO with a "nominal" beam, that is a single bunch of about 100 billion protons in this case.
This resulted in the ULO being 1 mm lower, so it is now 6 mm under the center of the tube. This might be enough.
:shifty:
...
Wow, don't mess with CERN people, they just burn away what gets in their way, either with excessively high electrical power or their giant proton gun. :axe:

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Tau 2
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Re: MUFO?

Post by Tau 2 » Fri Apr 24, 2015 6:10 am

Latest news:
I concluded that if they touched the beam when steering 6 mm down, the object would be there, butI forgot to take the thickness of the beam into account.
The official position of the object is: horizontally in the middle, vertically 9.6 mm below beam centre (which is about 8 mm high, counting from the bottom).
It is in beam 2. Lengthwise: about 25 640 meters (where they start counting at IR1).
Still no news if the opening is wide enough to leave the ULO lying there.

(You learn a lot on this forum. Even English verbs.)
- Tau

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