Modifications to DESY-II M. Minty Nov 11, 2003

The DESY-II 7GeV Lepton Synchotron DORIS f inj = 6.25 Hz E inj = 4.5 GeV N ppb = 5 · 10 9, typical DORIS f inj = 6.25 Hz E inj = 4.5 GeV N ppb = 5 · 10 9, typical PIA f inj = 50 Hz E = 450 MeV N ppb = (1-2) · PIA f inj = 50 Hz E = 450 MeV N ppb = (1-2) · PETRA-II f inj =3.125 Hz E inj = 7.0 GeV N ppb = 1.5·10 10, (typical) PETRA-II f inj =3.125 Hz E inj = 7.0 GeV N ppb = 1.5·10 10, (typical) focus of this presentation: requirements of PETRA-III on DESY-II and future plans

beam total number particles injection particles lifetime current of per bunch period per injected (hrs) (mA) bunches in PETRA (s) bunch * * * * * * * *10 9 Requirements on DESY-II for PETRA-III: PETRA-III tolerance on total current variation: 0.1 % PETRA-III tolerance on single-bunch current variation: 30 % injection frequency, initial fill 6.25 Hz wih N ppb =10 10 extraction beam energy 6 GeV extracted beam emittance ≤ 350 nm-rad with  p/p = top-up mode operation: improved reliability

Injection frequency, initial fill : f rep = 6.25 Hz with N ppb =10 10 f rep = 6.25 Hz, N ppb = 5 · 10 9, typical with e+ N ppb = 8 · 10 9, achieved with e+ N ppb > 10 10, typical with e- at E = 4.5 GeV (DORIS-mode) DESY-II transmission efficiency (>90%) seen to be independent of beam energy - same for DORIS-mode with E = 4.5 GeV and for PETRA-mode with E = 7.0 GeV no problems in DESY-II expected Extracted beam energy: E = 6.0 GeV E = 4.5 GeV < E = 6.0 GeV < E = 7.0 GeV (DORIS-mode) PETRA-III (PETRA-mode) no problems in DESY-II expected

Extracted beam emitance: ≤ 350 nm-rad with  p/p = using the present optics: E (GeV) Δf (kHz) ε (π nm-rad), design  p/p (10 -3 ) no problems in DESY-II expected (Δf is the presently-used frequency shift for beam loading compensation required for N ppb >1.5·10 10 ) An additional factor of ~ 2 reduction in horizontal emittance may be achievable with a higher phase-advance optics. The implications (e.g. costs and geometrical considerations) are being investigated. This possibility does not form part of the design concept for using DESY-II as an injector for PETRA-III.

Top-up mode operation following the suggestion of the MAC, tests of top-up mode operation at DORIS are underway: Tests #1 and #2 (23.10 and ): hand-triggered transfers at fixed current into specified bunches (check of timing synchrochronization and of the required “pre-triggers” for the pulsed elements; e.g kickers and septa) current in DORIS versus time

Tests #3 ( ): Automated transfers at fixed current into those bunches requiring additional current work in progress current in DORIS versus time software interface (total) intensity stability achieved: ~ 0.5% (compared to 0.1% required), fine-tuning required

Improved reliability As recommended by the committee, automated compilation of availability statistics including component failures and trend analysis (e.g. out-of-tolerance errors / early identification of changes in system availability) as required for PETRA-III will be implemented next year (an early start). In addition to ongoing accelerator maintenance and modernization, a few major (i.e. high-cost) infrastructural needs have been identified (for ensuring reliable operation of PETRA-III for the next decade): renewal/modernization of water cooling systems replacement of RF transmitter power feed systems upgrade of main synchrotron magnet power supplies As an injector for DORIS and HERA, the downtime attributable to the DESY-II (and DESY-III) accelerators has been so minimal that thorough study has not been warranted (remedial repairs take place between fills). “Critical access” (as required for beam operations to resume) is seen to be limited to once every few months (requiring ~2 hours maximum). work in progress

Future Plans: near-term: integration of new rf amplitude controls further top-up mode tests (including automated selection of desired bunch current) at DORIS at PETRA (?) preparation and demonstration of 6 GeV optics with Δf without Δf with mid-ramp extraction for DORIS resurrect emittance measurements continue investigation of higher phase-advance optics specification and integration of automated availability statistics far-future: hardware improvements mentioned above modernization of rf cavity interlocks replacement of corrector magnet power supplies development of satellite bunch monitor for DESY-II (possibly) separation of vacuum systems DESY-II / DESY-III