# Presentation: 118607

## RHIC BLM Performance during Run FY2002-03

- RHIC FY 2002-03 Retreat
- Mei Bai, Upton, NY 11973

## RHIC BLM Threshold System

- Blm viewing system

- Blm threshold system
-  slow threshold
-  to catch slow beam
-   losses (20 ms)
-  fast threshold
-  to catch fast beam
-   losses (0.1 ms)

## Typical RHIC Beam loss pattern

- Slow loss

- Fast  loss, this is also a typical
- Loss pattern for the yellow abort
- Kicker fire

## Threshold configuration during dAu Run

- At injection
- All masked ( both slow and fast threshold)
- At ev-accramp
- Activate only the phobos blms with slow threshold level set to 350 rad/hr
- 10 sec before transition
- In addition to the phobos blms, activate the blms around the IR regions with threshold level set to 8500 rad/hr

## Threshold configuration during dAu Run

- 100 sec before flattop
- Activate all the blms’ slow threshold except the following blms:
- Blms at beam dump area
- Blms at snakes and spin rotators
- Blms at rf cavities
- Blms at IPM and polarimeters
- Blms at pp2pp
- Except the phobos blms whose tripping level is kept at 350 rad/hr, all the other blms’ slow threshold level is set to 1500 rad/hr

## Threshold configuration during dAu Run

- At store
- The same as above except the phobos blms’ threshold level is lowered to 120 rad/hr
- At gap cleaning
- Mask all the blms around all IR regions to prevent blms from pulling permit with large debunched beam

## Threshold configuration during pp run

- At injection
- Blms at snakes are activated and set to120 rad/hr (slow) and 250 rad (fast)
- At accramp
- Activate the phobos blms and set to 350 rad/hr
- 116 sec before flattop
- All other blms are also activated and set to 1500 rad/hr except the blms at
- IPM and polarimeter
- Beam dump area
- At store
- Phobos blms trip level is lowered to 120   rad/hr

## What did we learn from the performance during RHIC FY02-03 run

- The blm slow threshold system is very effective in handling large slow beam losses (rise time >10ms)
- setting proper slow threshold trip level for snake blms significantly reduce the amount of snake quenches
- Can’t prevent magnet quench due to excessive beam losses caused by unbunched beam
- This happened a lot during Gap Cleaning, esp. before Feb 7. Afterwards, A special blm event (ev-blm4) was assigned to mask all the IR blms. One suppose to trigger this event  before gap cleaning to prevent the permit pull by blms due to large losses from gap cleaning. However,  there are still a few cases after Feb 7 when the permit pull during the gap cleaning because no ev-blm4 being triggered

## The slow threshold system can’t help preventing quenches due to very fast beam loss (< 5ms rise time) due to yellow abort kicker pre-firing at store or injection kicker mistiming at injection

Can’t help preventing quenches due to excessive beam losses due to improper beam dump

Some of the blm slow threshold trip levels need to be lowered to prevent magnet from quenching
Two cases during March when the magnet quenched due to large beam losses but blm failed to pull the beam permit

- Can’t help preventing quenches due to excessive beam losses due to improper beam dump
- Some of the blm slow threshold trip levels need to be lowered to prevent magnet from quenching
- Two cases during March when the magnet quenched due to large beam losses but blm failed to pull the beam permit

- What did we learn from the performance during RHIC FY02-03 run

## Large Beam Loss Caused Quench

- Could have been prevented if the
- trip level of this blm was set to
- 800 rad/hr

- May not be able to be prevented
- even if the trip level of this blm was
- set to 800 rad/hr because of the fast
- beam loss

## Phobos blms
From Feb 7 to Mar 24, Total 12 store/ramps were terminated due to the phobos blm pulling permit
Half of these could have been saved if we double the trip level for the phobos blms.

Snake blms and spin rotator blms
It has been demonstrated that the low slow threshold trip level is essential to avoid helical magnets from quenching

- From Feb 7 to Mar 24, Total 12 store/ramps were terminated due to the phobos blm pulling permit
- Half of these could have been saved if we double the trip level for the phobos blms.
- Snake blms and spin rotator blms
- It has been demonstrated that the low slow threshold trip level is essential to avoid helical magnets from quenching

- Bottle Necks of the Blm Slow Threshold

## Plan for next Run

- Readjust the slow threshold level for the blms based on the this run’s data
- Commission the fast loss threshold system
- How to handle the beam losses with rise time between 0.1 ms and 1 ms
- New threshold level for phobos blms if possible