# Presentation: 620892

##  Design and Tests of a New Rest Gas Ionization Profile Monitor Installed in the SPS as a Prototype for the LHCBIW04 May 3-6, 2004 –Knoxville, TennesseeC. Fischer, J. Koopman, D. Kramer, R. Perret, M. SillanoliCERN – Geneva - Switzerland

- C. Fischer-BIW04-May 3-6, 2004-Knoxville, Tennessee

## Acknowledgements

- AT/VAC/SL: monitor conditionings
- ES/MME & PH/TA1: coatings
- D. Cornuet and Co.:  magnet measurements
- G. Arduini: monitor insertion in SPS
- A. Beuret: magnet power supplies
- A. Guerrero: software requests
- B. Dehning, F. Roncarolo: wire scanner data
- and all others....

- C. Fischer-BIW04-May 3-6, 2004-Knoxville, Tennessee

## Outline

- The New Monitor
-                          *magnet*
*                         **central detector*
*                         **tank and assembly*
- Commissioning in 2002
- The year 2003
-                          *problems & cures*
*                         **results*
- Preparation & Perspectives for 2004

- C. Fischer-BIW04-May 3-6, 2004-Knoxville, Tennessee

## New  Rest Gas Monitor

- Encouraging results were got since the installation in 1999 of  a prototype provided by DESY and modified to use signal from electrons.
- It has been decided to equip the LHC with 4 gas monitors (one H, one V,   in each ring).
- Continuous profile measurements also needed in the SPS for the LHC era.
- Prototype design compatible with LHC requirements:
-                         **transverse** **space contingencies**  →     compactness
-                           **impedance budget**      →     no big discontinuities in the tank  smooth  transitions,
- e- signal → B field required
- Conventional magnet found with 200 mm gap,  fulfilling space requirements
- new gas monitor designed accordingly, manufactured in 2001 and installed in the SPS for the 2002 run

- C. Fischer-BIW04-May 3-6, 2004-Knoxville, Tennessee

## New  Rest Gas Monitor: the magnet (1)

- magnet recuperated from LEP with following characteristics:
-                      **I****max **** =                    55       A**
**                          ****B ****max****=                    0.25  T**** **
**                          ****Strength  =            0.14   Tm**
**                        ****Gap width :     200 x 200    mm****2**
**                        ****Overall length        680    mm**
-                   **section:           681 x 646     mm****2**
- hole drilled through the yoke for the light signal extraction

**3D view**

**top view**

**200 mm**

- C. Fischer-BIW04-May 3-6, 2004-Knoxville, Tennessee

## New  Rest Gas Monitor: the magnet

**%**

**%**

**Relative B variation along z with y=o at different x **

**Relative B variation along z with x=o at different y**** **

**B linearity**

**I (A)**

**B (mT)**

- C. Fischer-BIW04-May 3-6, 2004-Knoxville, Tennessee

## New  Rest Gas Monitor: mechanical designThe central detector

**166 **mm

**84 **mm

**cross section view**

**top view**

**3D view**

**e****-**

**light**

**MCP**

**prism**

**light**

- C. Fischer-BIW04-May 3-6, 2004-Knoxville, Tennessee

## New  Rest Gas Monitor: mechanical designThe tank within its magnet

**200 **mm

******=84 **mm

**Light signal**

**cross section view**

**3-D view**

**Light signal**

**680 **mm

**e****-**** ****signal**

**side view**

- C. Fischer-BIW04-May 3-6, 2004-Knoxville, Tennessee

##                New  Rest Gas Monitor

**Picture of the assembled central detector **

**As installed in the SPS **
**with 2 corrector magnets used at - B/2 (3 magnet bump)**

**Electric field map**

**e****_**

- C. Fischer-BIW04-May 3-6, 2004-Knoxville, Tennessee

## Results from commissioning in 2002 

-   encountered problems: high noise level
- electron cloud effect with LHC type beam
-                 evidence : signal increase after injection of 3rd batch
-             effect      : electrode DC voltage fluctuations →signal fluctuations
- high frequency modes generated by the LHC beam structure   inside the detector and in cables
-                  effect     : HV instabilities, signal loss
- remedies during 2003 stop
- NEG application (TiZrV) on HV electrodes to lower SEY
- RF absorbers  (filters) close to HV supplies
- series resistors close to detector feed-throughs
- view port conducting cover plate    installed for   better image
-                                                current conduction

- C. Fischer-BIW04-May 3-6, 2004-Knoxville, Tennessee

## The 2003 campaign (1)

- encountered problems and cures:
- bad electrical contacts on phosphor screen after bake-out at 200 C (needed for NEG activation)
-           insertion of thin CuBe frame with flexible contacts
- aging of MCP central region  due to high output signal
-      (test of a fast but less sensitive phosphor)
-          MCP gain decreased and image intensifier added,
-          bump applied to the beam orbit to avoid  bad area
- limited resolution
-           camera lens diaphragm opening reduced by 50%
- lightening on phosphor screen with shortest bunch length
-          series resistors removed
- image tilt  due to stray B field (through the magnet hole ) on the image intensifier
-            intensifier wrapped with  metal sheets
-             magnet used at 50% of B max

- C. Fischer-BIW04-May 3-6, 2004-Knoxville, Tennessee

## Results from 2003 (1)

**Pilot: 5.10****9**** p**

**Nominal: 3.5.10****13****p**

**= 0.88 mm**
**450 GeV**

**= 0.83 mm**
**E= 450 GeV**

- LHC type beams from pilot to nominal investigated; dynamic in current 104

******n****=3.5 10****-6**** m**

- C. Fischer-BIW04-May 3-6, 2004-Knoxville, Tennessee

## Results from 2003: analysis (3)

- limitations:
-           electron cloud effect still there (from 3rd batch) → signal increase
-              saturation of MCP at 450 GeV

**Profile Norm evolution along the cycle**

- C. Fischer-BIW04-May 3-6, 2004-Knoxville, Tennessee

## Results from 2003: analysis (4)

- Limitations, ct’n
-        limited resolution, **show-up at 450 GeV for low beam dimensions (s ****≤ ****0.7 mm)**

** ****75 ns LHC beam: ********n****= 1.4 10****-6**** m**

** ****pilot bunch: ********n****= 0.65 10****-6**** m**

**26 GeV – ******** ****IPM****= 1.5 mm**

**450 GeV -   ******** ****th**** ****IPM****        ****= 0.36 mm**
**                 ******** ****meas**** ****IPM   ****= 0.57 mm**

**450 GeV -   ******** ****th**** ****IPM****        ****= 0.53 mm**
**                   ******** ****meas**** ****IPM   ****= 0.64 mm **

**26 GeV – ******** ****IPM****= 2.2 mm**

**Error contribution: 0.35 ****m****m**
**Sources****:**     **intensifier **
**                          ****residual tilt **
**                          ****tails **
**                          ****optics: 247 ********m /pixel**

- C. Fischer-BIW04-May 3-6, 2004-Knoxville, Tennessee

## Cures implemented during the 2004 stop (1)

- Electron cloud:
-                       MCP input face NEG coated
- MCP aging and saturation:
-                       MCP replaced by a new one, will be operated at lower gain
-                           coupled with Low  Light Level camera →            lower MCP output current
-                           suppression of 2 stage amplification    →     better S/N ratio and resolution
-                           more sensitive phosphor layer on new prism: → lower MCP output current
-                                                                       CdS:In →Y3Al5O12:Ce (P46)
-                           variable gain to be applied during acceleration cycle → to avoid saturation
- Resolution limitation:
-                     general cleaning of different detector parts
-                           replacement of external RF absorbers close to power supplies
-                           number of wires on cathode grid decreased by factor 3 → contribution to tails
-                           non reflective treatment of support surfaces → to suppress parasitic reflections
-                           new optics  in front of the camera              →  improved opening

- C. Fischer-BIW04-May 3-6, 2004-Knoxville, Tennessee

## Cures implemented during the 2004 stop (3)

-                       new optical bench

**LLL**
**camera**

**PM tube**

- C. Fischer-BIW04-May 3-6, 2004-Knoxville, Tennessee

**With these improvements and a few other upgrades of the **
**control software, all efforts will made  during the year 2004 to bring the monitor to an operational stage for the LHC era**.
**A second monitor working in the H plane is approved and is expected for the 2006 SPS start-up.**** **

**Thank you for your attention**

- C. Fischer-BIW04-May 3-6, 2004-Knoxville, Tennessee