1 / 9

Running 2mrad IR in e-e- mode: BDS constraints

Running 2mrad IR in e-e- mode: BDS constraints. A.Seryi August 12, 2005. BDS constraints on e-e-. In 2mrad IR, the kick by the first quad on the outgoing beam is essential for extraction of the disrupted beam

jberry
Télécharger la présentation

Running 2mrad IR in e-e- mode: BDS constraints

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Running 2mrad IR in e-e- mode: BDS constraints A.Seryi August 12, 2005

  2. BDS constraints on e-e- • In 2mrad IR, the kick by the first quad on the outgoing beam is essential for extraction of the disrupted beam • The strength of FD (quads and sextupoles) is optimized to extract the disrupted beam properly, and this is optimized for e+e- • It means that, in e-e-, the FD strength has to stay the same as in e+e-, but with reversed sign of QD0, QF1, SD0, SF1 to provide exactly the same conditions for the extracted beam

  3. BDS constraints on e-e- • Thus, the sign of FD is reversed for the incoming beam, and the last quad is defocusing in Y for the incoming beam • Thus, in order to keep reasonable collimation depth, we have to increase the vertical beta function at the IP, as we will see, by about factor of 30 • The corresponding increase of Y beam size by factor of 5.5 is actually consistent with the desire to have reasonably wide deflection curve, for IP feedback • Thus, increasing betaY* may also be needed for 20mrad IR • The horizontal beta-function at IP is kept the same as in e+e-, to keep the beamstrahlung reasonable, but in principle betaX* can be somewhat decreased

  4. Tuning FF for e-e- • FD strength reversed • betaY* increased 30 times • Used only upstream quads to retune the optics, to keep the same geometry • The optics shown on the next pages is a draft version, its bandwidth is not good and there are geometrical aberrations left. But it can be further improved.

  5. FD for e+e- & e-e- by* = 9 mm bx* = 30 mm e-e- 2mrad IR Note also much larger dispersion in FD for e-e- e+e- 2mrad IR by* = 0.3 mm bx* = 30 mm

  6. Optics for e+e- & e-e- by* = 9 mm bx* = 30 mm e-e- 2mrad IR by* = 0.3 mm bx* = 30 mm e+e- 2mrad IR

  7. Chromaticity e-e- 2mrad IR Note that chromaticity is larger and much less local in e-e- e+e- 2mrad IR

  8. Ideal e-e- luminosity • For this optics, in ideal case, the GP calculated luminosity is 2.2E33 cm-2s-1 • This is 8% of the e+e- luminosity (2.8E34) • Spectrum of disrupted beam for e-e- is very similar as e+e- • May decrease sigma_x, but only slightly – to keep low E tail acceptable • GP parameters: • energy = 500 GeV • particles = 2.0 E10 • sigma_x = 554 nm • sigma_z = 300 um • emitt_x = 10 E-6m • emitt_y = 0.04 E-6m • beta_x = 30 mm • e-e- beta_y = 9 mm • e-e- sigma_y = 19.2 nm • e+e- beta_y = 0.3 mm • e+e- sigma_y = 3.5 nm

  9. Discussion • From the incoming and extraction optics point of view, e-e- in 2mrad IR is feasible • Optics constraints require reversing polarity of FD and thus increasing betaY* by about factor of 30 • The incoming FF optics is quite different than e+e- and would require retuning for e-e- option • The ideal e-e- luminosity is 2.2E33 cm-2s-1 (about 8% of e+e-) • The increased Y size also decreases the disruption of e-e- collisions • Keep X size similar as in e+e-, to minimize energy tail for extraction • Increasing betaY* (=> increasing Y size) is good for feedback and should also be done in 20mrad IR (where the in/out beamlines are independent and there are no such optics constraints)

More Related