Why So QUIET ??? Machine Development !!!!!

[gilgamorph]

hmm.. lets see... _ _

25 ns. . . . . new settings !! . . . . . . .

(what does 25ns mean if you are injecting one bunch ? just a doubled RF ?)

latest-news @ 12:04 - 288 b stable with high chromaticity

whew ....

by chromaticity are they refering to spread in kinetic energy in the bunch?

2) ATS !

there must be dozens, if not hundreds of random physics anagrams that match.

I go on record with a random guess of Advanced Tracking System.

Any praise ? _ _ _ _ . . . . . . or is it only scorn? _ _

( Although, come to think of it, an Anti-Tachyon Synchronizer might be handy. )

3) I was unable to watch the entire ultralow beta* squeeze

I gather that the target was beta*=0.10m at IP1 and IP5 and the OP Vistars view at LHC configuration seemed to indicate that an eight hour squeeze was unsuccessful. Beta* minned out at 0.55m. Although increased squeeze occurred IP2 (5.33->4.92->4.16) and at IP8 (3.14->3.07->2.81) the configuration page showed no change at IP1 and IP5.

After they lost beam1 (@ ~2:50) the operator commented:
@ 2:59:42 beta* = 14 cm Only for beam2 . . .
@ 3:13:40 ATS MD 10 cm beta* optics measurement

Does anyone know how quickly they were able to achieve beta*=0.55m ?

Any comments on why LHC Configuration page never showed the beta* values that the operator quoted ?

Does anyone have insight into the filling scheme nomenclature ?

_wp ?

_nLR ?

EXCELSIOR !

[chriwi]

Hi gilgamorph,

nice questions, unfortunately I can hardly answer any of them.

for the fillingscme so far:

single_3b_2_2_2_wp f.e. means:
| | | | | |
| | | | | --- I dont know
| | | | ------ 2 colliding bunchpairs in LHCb
| | | -------- 2 colliding bunchpairs in Alice
| | ---------- 2 colliding bunchpairs in Atlas & CMS (they are exactly oposite of eachotther)
| ------------ 3 bunches per beam
------------------ I dont know

[DCWhitworth]

Hi gilgamorph,

nice questions, unfortunately I can hardly answer any of them.

for the fillingscme so far:

single_3b_2_2_2_wp f.e. means:
| | | | | |
| | | | | --- I dont know
| | | | ------ 2 colliding bunchpairs in LHCb
| | | -------- 2 colliding bunchpairs in Alice
| | ---------- 2 colliding bunchpairs in Atlas & CMS (they are exactly oposite of eachotther)
| ------------ 3 bunches per beam
------------------ I dont know

I think the 'single' refers to the number of bunches per injection.

[pcatom]

OK Lets give it a go ....

25 ns. . . . . new settings !! . . . . . . .
(what does 25ns mean if you are injecting one bunch ? just a doubled RF ?)

25ns is the distance between 2 adjacent bunches which are delivered from the injectors. It only makes sense in multi-bunch injections. A maximum of 72 bunches can be created in the PS with a spacing of 25ns. 4 of these can be put together in the SPS to make 288 bunches in total. However between each batch of 72 bunches there is a slightly larger gap to allow clean transfer between the PS and SPS....

By the way, 25ns corresponds to a physical separation of 7.5m

latest-news @ 12:04 - 288 b stable with high chromaticity
whew .... by chromaticity are they refering to spread in kinetic energy in the bunch?

Chromaticity is the dependence of the focusing on momentum. In optical terms it is a little like chromatic aberration. There is always an energy spread in the bunch - therefore individual particles will see different focusing. In addition, due to synchrotron motion, the energy of each particle wil vary in time within the bunch..

2) ATS ! there must be dozens, if not hundreds of random physics anagrams that match.
I go on record with a random guess of Advanced Tracking System.

ATS: Achromatic Telescopic Squeeze.

3) I was unable to watch the entire ultralow beta* squeeze

I gather that the target was beta*=0.10m at IP1 and IP5 and the OP Vistars view at LHC configuration seemed to indicate that an eight hour squeeze was unsuccessful. Beta* minned out at 0.55m. Although increased squeeze occurred IP2 (5.33->4.92->4.16) and at IP8 (3.14->3.07->2.81) the configuration page showed no change at IP1 and IP5.
After they lost beam1 (@ ~2:50) the operator commented:
@ 2:59:42 beta* = 14 cm Only for beam2 . . .
@ 3:13:40 ATS MD 10 cm beta* optics measurement
Does anyone know how quickly they were able to achieve beta*=0.55m ?
Any comments on why LHC Configuration page never showed the beta* values that the operator quoted ?

Jeez there is a lot here ...
The ATS scheme uses a "classical" Squeeze technique to reach ~40cm then a very special distortion of the optics of the adjacent octants to lower it further (this does not compute correctly on the configuration page). 20cm was reached for both beams. Unfortunately 1 beam was lost in going to 10cm due to a setting error.

...the filling scheme seems to have been explained elsewhere ...

[gilgamorph]

Thanks Chriwi, DC.

I appreciate your insights pcatom, an excellent explanation.

25ns is the distance between 2 adjacent bunches which are delivered from the injectors. It only makes sense in multi-bunch injections.

Sorry, I was facetiously riffing on the single bunch pilot probe that they injected. I'm glad to learn about the PS/SPS limitations on bunch length. It explains their excitement at 288 bunch injections - that much closer to maximum possible luminosity!

Your comments on chromaticity and ATS were succinct and much appreciated.

re: filling scheme; Chriwi and DCWhitworth elucidated the parts I knew. I was looking for an explanation of the postfaces seen in recent weeks that I've no clue about. Current fills end in _wp and prior to TS2 there was a fill with _nLR at the end of the AFS.

Again, Thanks Greatly for your assistance.