ISOLDE Interlocks

KH

MSWG 13 August 2013

K. Hanke, E. Piselli

Wrong Beam to ISOLDE

2

liquid metal target: cracked container welds (sent normal beam instead of staggered)

converter target: twisted W convertor rod (sent standard focus with high intensity instead of waist with low intensity)

certain ISOLDE targets have upper limits for theaverage and for the bunch intensity

different ISOLDE targets require different focalsettings and beam steering

in 2009 we introduced a number of interlocks

KH

ISOLDE Interlocks Overview

1. watchdog: stop the beam in case of beam loss in the BTY line

2. type of beam (select ‘normal’ or ‘staggered’, others not executed)

3. focal settings: stop the beam in case the settings of the last two quadrupoles before the target deviate from the ones set by the ISOLDE machine supervisor

4. steering: stop the beam in case the settings of the last two steerers before the target deviate from the ones set by the ISOLDE machine supervisor

5. average intensity: stop the beam in case the average beam current exceeds the one set by the ISOLDE machine supervisor (absolute max 2 uA!)

6. intensity per bunch: stop the beam in case the bunch current exceeds the one set by the ISOLDE machine supervisor

KH

ISOLDE Watchdog

measurement of beam current after PSBrecombination and before targetinterlock condition:difference in beam intensity <300E10manual reset by the PSB operatorneededthis is to protect the BTY line from irradiation, not related to ISOLDE itself

KH

ISOLDE Beam Types

“normal” beam:up to full intensity 4E13 pppup to 4 rings = 4 bunches used for solid targets, often UCbunch spacing 586 nsusers NORMGPS & NORMHRS

“staggered” beam:low intensity, depending on target3 rings = 3 bunchesused for liquid metal targetsbunch spacing 16 ususer STAGISO

ISOLDE Focal Settings on Target

‘standard’ focus - up to full intensity- steered on target

‘waist’ on target (converter targets)- low intensity- steered on converter

KH

ISOLDE Focal Settings on Target

focal settings of the proton beam depend on the type of target they will are set by the ISOLDE machine supervisor after each target change settings must not change any more during that particular runfocus interlock condition:setting(device)-2 A ≤ AQN(device) ≤ setting(device)+2 A

KH

ISOLDE Steering on Targets

steering of the proton beam is done by the ISOLDE machine supervisor foreach individual target (proton scan) and settings must not change any more during that particular runposition interlock condition:setting(device)-1 A ≤ AQN(device) ≤ setting(device)+1 A

KH

Average Proton Intensity (“PPS”)

maximum pps value of the proton beam is entered by the ISOLDE machine supervisor for each individual target and settings must not change any more during that particular runpps interlock condition:average 2’(AQN(device)) ≤ MAX PPSabsolute maximum value 2 uA except special permission from RP (radiation levelof extracted air) KH

Proton Bunch Intensity (“PPP”)

maximum ppp value of the proton beam is entered by the ISOLDE machine supervisor for each individual target and settings must not change any more during that particular runppp interlock condition:I(300)≤ MAX ppp

275 300 805 1200

Int.

[pp

p]

t [ms]0

I(300)

KH

Interlock Actions

ppp: cuts RF and comes automatically back as soon as the conditions are OKacts on the cycle which is being executed

pps, position, focus:stops beam in the Linac;comes automatically back as soon as the conditions are OKacts on next cycleuses SIS

watchdog:manual reset needed

KH

Configuration GUI

12

only ISOLDE machine supervisors are authorised to change settingshowever GUI is not password protected, in principle accessible by everybody fromthe console manager

• waist• standard

KH

• NORMHRS• NORMGPS• STAGISO

ISOLDE Vistar

KH

displayed in the CCC and ICR

Summary

• In the past there were occasional critical incidents (wrong beam sent, wrong focusing or steering after reloading archives etc.)

• a number of interlocks have been put in place in 2009• interlocks use standard CERN technology (SIS)• since then no more incident• interlock conditions change from run to run; the ISOLDE machine

supervisor is the only person authorised to manipulate the interlock settings

• the ISOLDE Vistar has been redone in order to display the relevant parameters in both the CCC and the ICR