TY  - CONF
AU  - Keil, J.
AU  - Sahoo, G.
AU  - Wanzenberg, R.
AU  - Novokshonov, A.
AU  - Kube, G.
AU  - Falkenberg, G.
AU  - Chae, Yong-Chul
AU  - Ebert, Michael
TI  - Microwave instability and energy spread measurement via vertical dispersion bump in PETRA III
M1  - PUBDB-2018-02057
PY  - 2018
AB  - The recent measurement of bunch length versus current indicated  that  the  longitudinal  impedance  (Z/n)  is  0.15 Ohm in close agreement with the impedance model [1]. Naïve application of Keil-Schnell criteria predicts that the threshold of microwave instability at 0.25 mA. Since the single  bunch  intensity  is  in  the  range  of  0.2  –  2.5  mA depending on the fill pattern of PETRA III, we expect to observe the fill-pattern dependent energy spread according  to  the  theory.  However,  the  3rd  generation  light sources comparable to PETRA III often reported the observation  which  was  much  greater  than  the  theoretical one.  In order to induce the beam size variation we had used skew quadrupoles to generate the dispersion in vertical plane. In particular we made dispersion bump at the undulator sector so that we were able to use the x-ray optics for the precise determination of small vertical beam size. In this paper we report the experimental setup and measurement  data  with  the  estimate  on  the  instability threshold. We also report the vertical emittance and energy spread based on the x-ray beam size measurement as well as the rf signal which was excited by the beam at the longitudinal feedback cavity.
T2  - 9th International Particle Accelerator Conference
CY  - 29 Apr 2018 - 4 May 2018, Vancouver (Canada)
Y2  - 29 Apr 2018 - 4 May 2018
M2  - Vancouver, Canada
LB  - PUB:(DE-HGF)24
UR  - https://bib-pubdb1.desy.de/record/403389
ER  -