--- title: Critical Beam Dumps description: Here a list of all uncontrolled / critical beam dumps is kept template: main.html --- **Categories of uncontrolled beam dump events** * 1 - Distributed loss of < 50 mA * 2 - Distributed loss of > 50 mA * 3 - Localized loss of < 50 mA * 4 - Localized loss of > 50 mA * 5 - Shutdown required | **Category** | **Amount detected** | | :- | :- | | 1 | 1 | | 2 | 11 | | 3 | 0 | | 4 | 6 | | 5 | 0 | | Total | 16 | ## 18 - Mon 08-Jun-26 20:02 * BDC Triggered by **LLRF for Storage Ring Cavity 1** at **404 mA** * **Root cause:** Misfiring of kicker 3 from injection 4-kicker bump * **Issue:** Uncontrolled loss of 400 mA in straight X02 * **Category:** 4 * [https://elog-gfa.psi.ch/SLS/64543](https://elog-gfa.psi.ch/SLS/64543) * [https://elog-gfa.psi.ch/SLS/64538](https://elog-gfa.psi.ch/SLS/64538) * [https://elog-gfa.psi.ch/SLS/64529](https://elog-gfa.psi.ch/SLS/64529) * [https://elog-gfa.psi.ch/SLS+RF/2263](https://elog-gfa.psi.ch/SLS+RF/2263) ## 17 - Tue 14-Apr-26 10:49 * BDC Triggered by **LLRF for Storage Ring Cavity 4** at **300 mA** * **Root cause:** Misfiring of injection 4-kicker bump due to EVR output mapping misalignment * **Issue:** Uncontrolled loss of 300 mA downstream of X01 * **Category:** 4 * [https://elog-gfa.psi.ch/SLS/63797](https://elog-gfa.psi.ch/SLS/63797) * [https://elog-gfa.psi.ch/SLS+RF/2209](https://elog-gfa.psi.ch/SLS+RF/2209) ## 16 - Mon 08-Dec-25 09:02 * BDC Triggered by **LLRF for Storage Ring Cavity 4** at **403 mA** * **Root cause:** Misfiring of injection 4-kicker bump during top up due to Red Pitaya issue * **Issue:** Uncontrolled loss of 403 mA downstream of X01 * **Category:** 4 * [https://elog-gfa.psi.ch/SLS/62799](https://elog-gfa.psi.ch/SLS/63420) * [https://elog-gfa.psi.ch/SLS+RF/2178](https://elog-gfa.psi.ch/SLS+RF/2178) ## 15 - Sun 12-Oct-25 12:41 * BDC Triggered by **LLRF for Storage Ring Cavity 2** at **400 mA** * **Root cause:** unknown * **Issue:** Uncontrolled loss of 400 mA at unknown location * **Category:** 2 * Beam lost over ~700 ms * [https://elog-gfa.psi.ch/SLS/62799](https://elog-gfa.psi.ch/SLS/62799) * [https://elog-gfa.psi.ch/SLS+RF/2140](https://elog-gfa.psi.ch/SLS+RF/2140) ## 14 - Mon 06-Oct-25 18:36 * BDC Triggered by **LLRF for Storage Ring Cavity 3** at **402 mA** * **Root cause:** Classical ion instability due to bad vacuum in X02SA with U15 gap closed * **Issue:** Uncontrolled loss of 400 mA at thin septum and collimators * **Category:** 2 * Filling gap of 50 buckets and vacuum interlock at 1e-7 mbar * Vacuum interlock is triggered but far too late with 200 ms delay * [https://elog-gfa.psi.ch/SLS/62668](https://elog-gfa.psi.ch/SLS/62668) * [https://elog-gfa.psi.ch/SLS+RF/2135](https://elog-gfa.psi.ch/SLS+RF/2135) ## 13 - Sat 04-Oct-25 17:09 * BDC Triggered by **LLRF for Storage Ring Cavity 2** at **402 mA** * **Root cause:** unknown * **Issue:** Libera data indicates uncontrolled beam loss * **Category:** 2 * RadFET indicates controlled beam loss * [https://elog-gfa.psi.ch/SLS/62639](https://elog-gfa.psi.ch/SLS/62639) ## 12 - Tue 30-Sep-25 13:55 * BDC Triggered by **Orbit Deviation** at **53 mA** * **Root cause:** unknown * **Issue:** Uncontrolled beam loss at thin septum * **Category:** 1 * happened during MD [kw40](https://sls.psi.ch/schedule/#2025-kw40) * [https://elog-gfa.psi.ch/SLS/62568](https://elog-gfa.psi.ch/SLS/62568) ## 11 - Mon 29-Sep-25 17:18 * BDC Triggered by **Vakuum** at **385 mA** * **Root cause:** Misfiring of 4 kicker bump K1 and K2 during accumulation * **Issue:** Uncontrolled loss of 385 mA at thin septum * **Category:** 4 * VCS: ARS01 VPIC 0010 :PUMP1-PRESSURE * [https://elog-gfa.psi.ch/SLS/62552](https://elog-gfa.psi.ch/SLS/62552) ## 10 - Sun 28-Sep-25 11:10 * **Root cause:** Vacuum in injection straight * **Issue:** Uncontrolled loss of 400 mA at thin septum * **Category:** 2 * VCS: ARS01 VPIC 0010 :PUMP1-PRESSURE * Beam lost over ~500 ms * not clear since RadFET indicates good dump and while Libera loss data does not agree * steep drop of lifetime before beam loss also indicates uncontrolled beam loss since usually faster than vacuum interlock * [https://elog-gfa.psi.ch/SLS/62525](https://elog-gfa.psi.ch/SLS/62525) ## 9 - Fri 26-Sep-25 03:37 * **Root cause:** Classical ion instability due to bad vacuum in X02SA with U15 gap closed * **Issue:** Uncontrolled loss of 400 mA at thin septum and collimators * **Category:** 2 * Filling gap of 50 buckets and vacuum interlock at 1e-7 mbar * Vacuum interlock is triggered but far too late with 230 ms delay * [https://elog-gfa.psi.ch/SLS/62668](https://elog-gfa.psi.ch/SLS/62492) ## 8 - Thu 25-Sep-25 22:58 * **Root cause:** Classical ion instability due to bad vacuum in X02SA with U15 gap closed * **Issue:** Uncontrolled loss of 400 mA at thin septum and collimators * **Category:** 2 * Filling gap of 30 buckets and vacuum interlock at 4e-7 mbar * From now on: * Vacuum Interlock threshold now reduced to 1e-7 mbar * Filling pattern gap increased from 30 to 50 buckets * [https://elog-gfa.psi.ch/SLS/62484](https://elog-gfa.psi.ch/SLS/62484) ## 7 - Thu 25-Sep-25 18:04 * **Root cause:** Classical ion instability due to bad vacuum in X02SA with U15 gap closed * **Issue:** Uncontrolled loss of 400 mA at thin septum and collimators * **Category:** 2 * Beam dump seems to be caused by an initially slow-rising vacuum spike inside the X02SA U15 undulator * Lifetime went down from 8 hours to <2 hours slowly in the last 5 minutes before the beam dump simultaneously with the pressure going up * The observed vacuum spike could be a classical ion instability * Vacuum Interlock unfortunately was not triggered * ID gap is stuck at minimum value and cannot be opened which would improve the vacuum * [https://elog-gfa.psi.ch/SLS/62480](https://elog-gfa.psi.ch/SLS/62480) * [https://elog-gfa.psi.ch/SLS/62482](https://elog-gfa.psi.ch/SLS/62482) ## 6 - Tue 23-Sep-25 15:56 * **Root cause:** FOFB writes bad values to correctors * **Issue:** Uncontrolled loss of 388 mA * **Category:** 2 * Happened during BPM Sector reboot, i.e., overall reliability issue with BPM/FOFB system * Beam dump controller only triggered by RF stations * Post mortem data clearly shows that beam was lost before dump kicker was fired * Communication issue between machine experts concerning disabling the orbit deviation beam dump seems irrelevant * It would be good if the disabling and reenabling of the orbit deviation beam dump for sector reboots could be automized in a safe way * [https://elog-gfa.psi.ch/SLS/62451](https://elog-gfa.psi.ch/SLS/62451) * [https://elog-gfa.psi.ch/SLS+RF/2121](https://elog-gfa.psi.ch/SLS+RF/2121) ## 5 - Thu 07-Aug-25 20:31 * **Root cause:** misfiring of one individual beam dump kicker stage * **Issue:** Uncontrolled loss of 400 mA * **Category:** 4 * it seems one stage of the beam dump kicker misfired, partially killing the beam and triggering an RF interlock which requested a beam dump which led to a intended firing of the beam dump kicker that failed for the only just misfired stage * [https://elog-gfa.psi.ch/SLS/61987](https://elog-gfa.psi.ch/SLS/61987) * [https://elog-gfa.psi.ch/SLS/62030](https://elog-gfa.psi.ch/SLS/62030) ## 4 - Tue 29-Jul-25 16:43 * **Root cause:** Fast change of quadrupole setpoints (MD shift) * **Issue:** Uncontrolled loss of 200 mA * **Category:** 2 * Fast orbit detection might prevent this in future but not if tune moved to 0.5 * [https://elog-gfa.psi.ch/SLS/61837](https://elog-gfa.psi.ch/SLS/61837) ## 3 - Tue 29-Jul-25 15:51 * **Root cause:** Fast change of quadrupole setpoints (MD shift) * **Issue:** Uncontrolled loss of 140 mA * **Category:** 2 * Fast orbit detection might prevent this in future but not if tune moved to 0.5 * [https://elog-gfa.psi.ch/SLS/61836](https://elog-gfa.psi.ch/SLS/61836) ## 2 - Wed 23-Jul-25 16:32 * **Root cause:** FOFB wrote NAN to corrector magnets * **Issue:** Uncontrolled loss of 400 mA * **Category:** 2 * Automated testing clearly shows the bug of the EPICS ringbuffer record in EPICS 7.0.8 leading to the regular appearance of huge numbers about every 5 seconds when writing a new value to the ringbuffer with 10 Hz. The bug is not observed at all for EPICS 7.0.9 * [https://elog-gfa.psi.ch/SLS/61782](https://elog-gfa.psi.ch/SLS/61782) * [https://elog-gfa.psi.ch/SLS/61768](https://elog-gfa.psi.ch/SLS/61768) ## 1 - Tue 13-May-25 09:36 * **Root cause:** Misfiring of individual kicker during turning off 4 Kicker Bump at 400 mA * **Issue:** Uncontrolled loss of 400 mA * **Category:** 4 * EPICS procedure to prevent this is implemented * [https://elog-gfa.psi.ch/SLS/60877](https://elog-gfa.psi.ch/SLS/60877) * [https://elog-gfa.psi.ch/SLS/60878](https://elog-gfa.psi.ch/SLS/60878)