LHC Days 2001 Villars-sur-Ollon, Massimiliano Ferro-Luzzi, CERN/EP Overview of LHCb Current VELO design:  Mechanics  Cooling system for Si detectors  Vacuum issues  RF issues Road map Summary and outlook LHCb and its VErtex LOcator integration into the LHC

LHC Days 2001 Villars-sur-Ollon, Massimiliano Ferro-Luzzi, CERN/EP (t = proper time; a bar stands for “CP conjugate”) A Large Hadron Collider beauty experiment for precision measurements of CP violation and rare decays A Large Hadron Collider beauty experiment for precision measurements of CP violation and rare decays Measure asymmetries: A f (t) = R f (t) + R f (t) R f (t) - R f (t) from four rates R f (t) = initial B decaying to final state f e.g. (semi)leptonic B-decays.  Flavour Changing Neutral Currents

LHC Days 2001 Villars-sur-Ollon, Massimiliano Ferro-Luzzi, CERN/EP B0  +-B0  +- LHCb: identify B-mesons and their age at decay Crucial information: particle ID, 1 ary and 2 ary vertices vertex detector used in trigger level-1 offline decay distance resolution  120  m (proper decay time resolution  0.04 ps) Primary vertex 10 mm Typical event for LHCb Typical event for LHCb Generated polar angles of b and b hadrons (with PYTHIA) B 0   - D *+  D 0  +

LHC Days 2001 Villars-sur-Ollon, Massimiliano Ferro-Luzzi, CERN/EP LHCb Detector “original” IP8displaced IP8 Acceptance:   mrad Bakeable NEG- coated beam pipe Subsystems can be retracted from conical beam pipe Warm dipole: -  B dz  4 Tm - correction scheme - ramp with LHC - reverse polarity

LHC Days 2001 Villars-sur-Ollon, Massimiliano Ferro-Luzzi, CERN/EP detector prototype 300  m thick Si single-side n-on-n Design work ongoing for front-end chip ( DMILL and sub  technologies) total of 220 k channels, analogue, S/N=15 one module: r and  measuring planes with stereo angle small overlap between opposite halves for alignment and acceptance cool down: -25 < T operate < +10 o C come as close as possible to LHC beams minimise material between vertex and first hit on Si  put detectors in vacuum large outgas rates of detector components  separate detectors from LHC vacuum 300  m thick Si single-side n-on-n Design work ongoing for front-end chip ( DMILL and sub  technologies) total of 220 k channels, analogue, S/N=15 one module: r and  measuring planes with stereo angle small overlap between opposite halves for alignment and acceptance cool down: -25 < T operate < +10 o C come as close as possible to LHC beams minimise material between vertex and first hit on Si  put detectors in vacuum large outgas rates of detector components  separate detectors from LHC vacuum [cm] 0 towards spectrometer Z retract by  3 cm during beam filling/tuning LHCb Si Vertex Locator Modules r|r| rr r|r| etc mm r 

LHC Days 2001 Villars-sur-Ollon, Massimiliano Ferro-Luzzi, CERN/EP VELO mechanical design Cooled Si sensors in secondary vacuum Openings for feedthrough flanges (25’000 pins) 25 cm 120 cm Exit window mm thick Al RF/Vacuum thin shield Vertex detector half Decouple access to silicon detectors from access to primary vacuum Baking up to 150 o C is possible Use ultrapure neon venting VELO and NEGs need not be rebaked after access to Si detector

LHC Days 2001 Villars-sur-Ollon, Massimiliano Ferro-Luzzi, CERN/EP Mixed-phase CO 2 Cooling system Advantages: Radiation hard (used in nuclear power plants) Non toxic (conc. < 5%), non flammable Low pressure drop in microchannel tubes Good thermodynamic properties Widely available at low cost No need to recover or recycle Principle of operation: CO 2 is used in a two-phase cooling system. The coolant is supplied as a liquid, the heat is taken away by evaporation. LHCb VELO: in total, ~ 54  40 W of heat, each cooled by a pipe of OD=1.1/ID=0.9 mm. Tested at NIKHEF: See LHCb /VELO capacity of cooling pipe > 50 W heat transfer coefficient between pipe and coolant > 2 W cm -2 K -1 Phase diagram CO Temperature [°C] Pressure [bar] vapor liquidsolid gas critical point triple point

LHC Days 2001 Villars-sur-Ollon, Massimiliano Ferro-Luzzi, CERN/EP CO 2 Cooling Tubes Total amount of CO 2 in the system  6 of liquid  3 m 3 of gas at STP In the 2 ary vacuum volume:  100 m  100 g of liquid  30 of gas at STP  50 mbar in 600 at T room Total amount of CO 2 in the system  6 of liquid  3 m 3 of gas at STP In the 2 ary vacuum volume:  100 m  100 g of liquid  30 of gas at STP  50 mbar in 600 at T room OD = 1.1 mm, ID = 0.9 mm vacuum brazed (no flux, no fittings) can sustain p > 300 bar (CO 2 : p equilib = 72 bar at 30 o C) OD = 1.1 mm, ID = 0.9 mm vacuum brazed (no flux, no fittings) can sustain p > 300 bar (CO 2 : p equilib = 72 bar at 30 o C) Flow restrictions

LHC Days 2001 Villars-sur-Ollon, Massimiliano Ferro-Luzzi, CERN/EP CO 2 Cooling system layout Standard refrigerator unit Behind shielding wallHall area2 ary vacuum Storage vessel Liquid CO 2 pump Heat exchanger Restriction (  0.85mm*40 mm) Needle valve(sets total flow) Pressure regul. valve (70 bar) Shutter valve Cooling tubes (  0.9/1.1 mm) Gas return (  12mm) ~ 60 m Liquid supply (  6mm) Control pressure (i.e. temp.)

LHC Days 2001 Villars-sur-Ollon, Massimiliano Ferro-Luzzi, CERN/EP bellows chain/belt cooling/bake out gearbox 1:40 ball spindle 16x2 10 mm linear bearing 2x 30 mm motor Detectors halves opened/closed by remote-controlled step motors vert. = 10 mm, horiz. = 2x30 mm Microswitches at out position Monitor with LVDTs Alignment to nominal beam axis : 2 planes, 3 points each, define IP Steel frame, with alignment pins for reproducible coupling All motors, bearings, gearboxes, etc., are outside the vacuum Support and motion mechanics 30 mm

LHC Days 2001 Villars-sur-Ollon, Massimiliano Ferro-Luzzi, CERN/EP Detector housings = 2 ary vacuum vessels Use rectangular membranes for lateral motion and thin-walled Al box for guiding mirror charge RF shielding vacuum boundary 1 ary /2 ary Need not withstand atmospheric differential pressure. Still, fabrication difficult and costly ! Use rectangular membranes for lateral motion and thin-walled Al box for guiding mirror charge RF shielding vacuum boundary 1 ary /2 ary Need not withstand atmospheric differential pressure. Still, fabrication difficult and costly !  15 mm  3 mm Remove upstream flange for mounting (need ~2 m access from IP) Seals: 1 ary / air: all metal 1 ary / 2 ary : viton & metal 2 ary / air: viton & metal

LHC Days 2001 Villars-sur-Ollon, Massimiliano Ferro-Luzzi, CERN/EP Install wake field suppressors after mounting 2 ary vacuum container Upstream is “easy”: mounted with large flange off Downstream is more delicate: mount through top flanges Install wake field suppressors after mounting 2 ary vacuum container Upstream is “easy”: mounted with large flange off Downstream is more delicate: mount through top flanges Wake field suppressors Aim: Provide a continuous conducting wall throughout the VELO to guide the mirror charge Aim: Provide a continuous conducting wall throughout the VELO to guide the mirror charge

LHC Days 2001 Villars-sur-Ollon, Massimiliano Ferro-Luzzi, CERN/EP Wake field suppressors 194mm Thickness: 100  m Current design: Up/downstream suppressors are identical Material: CuBe (anneal, form, harden at 400 o C) 16 segments (which deform differently during movement) Coat suppressors (?) Press-fit to beam pipe Mounting to detector box is non-trivial

LHC Days 2001 Villars-sur-Ollon, Massimiliano Ferro-Luzzi, CERN/EP LHCb VELO - LHC machine integration issues The LHCb vertex detector system should not hamper LHC operation Address: vacuum issues  static and dynamic vacuum (ions, electrons and photons)  calculations and test measurements radio-frequency issues  high frequency modes, losses, coupling impedance  calculations and test measurements safety issues  define level of acceptability  perform risk analysis

LHC Days 2001 Villars-sur-Ollon, Massimiliano Ferro-Luzzi, CERN/EP Wake field simulations Aim: acceptable heat dissipation in the VELO minimize coupling impedance Performed MAFIA simulations (frequency domain): full tank model and smaller models detector halves in position open and closed compared various detector encapsulations with different corrugation shape and depth deal with complex non-symmetric structure! time-consuming and CPU intensive LHCb “A first study of wake fields in the LHCb VD” LHCb “W. f. in the LHCb VD: strip shielding” LHCb “W. f. in the LHCb VD: alternative designs for the w. f. suppr.” N. van Bakel VU Amsterdam

LHC Days 2001 Villars-sur-Ollon, Massimiliano Ferro-Luzzi, CERN/EP Frequency (MHz) Shunt resistance (  ) d=160mm d=20mm d=5mm 100 W limit d Beam axis Si sensors Al shield ~35mm Conclusion: no problematic resonant effects for corrugated encapsulation with corrugation depth d < 20 mm Under study: time domain ( ABCI & MAFIA ) low frequency slope of Im(Z // ) loss factor k // Wake field simulations (continued)

LHC Days 2001 Villars-sur-Ollon, Massimiliano Ferro-Luzzi, CERN/EP RF tests at NIKHEF First 3 measured eigenmodes of empty tank: 220, 270, 320 MHz Compare to simulation with MAFIA Study: Eigenmodes, impedance Z // Effect of WF screens, open/close halves RF fields inside secondary vacuum (pick-up) Use: Wire method Multiple (rotatable) loop antennas Reference LHC pipe 222 MHz 272 MHz320 MHz

LHC Days 2001 Villars-sur-Ollon, Massimiliano Ferro-Luzzi, CERN/EP Vacuum constraints for stable pressure in VELO: a first glance LHC beam-gas life time limit   24 h requires LHC integrated density t max  1  H 2 /cm 2. H 2 pressure of mbar  2 m (300K) corresponds to  0.005% of t max.  rather “loose” constraint for stable pressure in VELO mbar  1.2 m (H 2 300K)  1.5 % of LHCb nominal luminosity More serious: pumping life time of NEG s in LHCb beam pipe. Estimate: p CO  mbar  6 m of pipe saturated in ~3 months (?)

LHC Days 2001 Villars-sur-Ollon, Massimiliano Ferro-Luzzi, CERN/EP Dynamic Vacuum Dynamic vacuum phenomena must be taken into account in the design of the LHCb vacuum system (including VELO): Ion-, electron- and photon-induced desorption Electron multipacting  stringent constraints on geometry and surface desorption properties, e.g. for ion-induced desorption: local pumping speed and surface materials must be chosen such that the critical current I crit > 2  2  0.85 A = 3.4 A Safety factor two beams

LHC Days 2001 Villars-sur-Ollon, Massimiliano Ferro-Luzzi, CERN/EP Dynamic pressure profile p (torr) Unbaked VELO tank  i as for unbaked metal ion desorption yield (incident ion energy  E ion  ~ 300 eV) LHCb beam pipe (NEG saturated, i.e. not pumping)  i as for baked surface Comments: new VELO design is bakeable  less outgassing and beam-induced desorption  NEGs not saturated most of CO x desorption in this calculation is photon-induced  if needed: reduce locally the photon flux A. Rossi, LHC-VAC No electron-induced desorption in the model

LHC Days 2001 Villars-sur-Ollon, Massimiliano Ferro-Luzzi, CERN/EP VELO vacuum system Differential pumping system: – No valves between VELO 1 ary vacuum and LHCb NEG -coated beam pipe – VELO 1 ary vacuum base pressure (no beam) ~10 -9 mbar – Detectors in 2 ary vacuum ~10 -4 mbar Separation 1 ary /2 ary vacuum by thin Al foil – Developing gravity-controlled safety valve to protect the foil against differential pressure – Coat foil with NEG or titanium if needed (see dyn. vac. phenomena) Access to Si detectors decoupled from access to primary vacuum – In-situ baking of primary vacuum surfaces up to 150 o C – Use ultrapure neon venting so that VELO and NEG s need not be rebaked after access to Si detector Working on a detailed description of the VELO vacuum system: – components (pumps, ducts,...) – monitoring and safety equipment – control system (PLC based) – describe static and transient modes

LHC Days 2001 Villars-sur-Ollon, Massimiliano Ferro-Luzzi, CERN/EP Vacuum System

LHC Days 2001 Villars-sur-Ollon, Massimiliano Ferro-Luzzi, CERN/EP Thin vacuum foil Beryllium (1 mm thick): very expensive… if at all feasible! safety issues Aluminium (250  m thick): “cheap & readily available” (compared to Beryllium) NIKHEF: extensive prototyping program, welded 100  m on 300  m Labour intensive: manufacture moulds, make foils, ~12 press/anneal cycles, etc. Max  p  500 mbar* Max  p  15 mbar* * Means irreversible deformation, no safety factor included. Values are approximate as mechanical properties can deviate substantially for the actual foil (hence, tests on prototypes are needed).

LHC Days 2001 Villars-sur-Ollon, Massimiliano Ferro-Luzzi, CERN/EP Thin vacuum foil (0.25 mm Al)

LHC Days 2001 Villars-sur-Ollon, Massimiliano Ferro-Luzzi, CERN/EP VELO material distribution X/X 0 seen by particles azimuthal angle  Polar angle or pseudo-rapidity Average  X/X0  = 18.9 % (was 8% in TP) Main problems: - photon-originated showers - degradation of electron momentum resolution

LHC Days 2001 Villars-sur-Ollon, Massimiliano Ferro-Luzzi, CERN/EP Gravity-controlled valve weight ~ few grams, area ~ few cm 2 reacts to differential pressure ~ few mbar no electrical power no pressurized air intrinsically safe solution to 1 ary vacuum to 2 ary vacuum to auxiliary pump Use tandem valve to protect against both possible signs of differential pressure

LHC Days 2001 Villars-sur-Ollon, Massimiliano Ferro-Luzzi, CERN/EP Risk Analysis Purpose: To provide an objective basis for a constructive and methodical evaluation of the VELO design. comprehensive overview of all risks involved what risk scenarios, what consequences, what probabilities to occur ? requirements/recommendations for a given design choice what tests should be performed and what results obtained to make the chosen option acceptable ? basis for a later, more detailed risk analysis f.i. risk of “injuries to personnel” are not assessed in details, but believed to be  downtime and equipment loss

LHC Days 2001 Villars-sur-Ollon, Massimiliano Ferro-Luzzi, CERN/EP Framework of Risk Analysis Use same model as for CERN Safety Alarms Monitoring System (CSAMS) (1) Identify undesired event (UE) (2) Determine the consequence category of UE (3) Use predefined table to fix maximum allowable frequency (MAF) (4) Determine required frequency by reducing MAF by factor 100

LHC Days 2001 Villars-sur-Ollon, Massimiliano Ferro-Luzzi, CERN/EP Framework: frequency categories Indicative frequency CategoryDescription level (per year) Frequent Events which are very likely to occur > 1 in the facility during its life time Probable Events which are likely to occur in the facility during its life time Occasional Events which are possible and expected to occur in the facility during its life time Remote Events which are possible but not expected to occur in the facility during its life time Improbable Events which are unlikely to occur in the facility during its life time Negligible Events which are extremely unlikely to < occur in the facility during its life time

LHC Days 2001 Villars-sur-Ollon, Massimiliano Ferro-Luzzi, CERN/EP Framework: consequence categories Equipment CategoryInjury to personnelloss in CHFDowntime (indicative)(indicative) (indicative) CatastrophicEvents capable of resulting> 10 8 > 3 months in multiple fatalities Major Events capable of resulting week to 3 months in a fatality Severe Events which may lead hours to 1 week to serious, but not fatal injury Minor Events which may lead < 4 hours to minor injuries Turns out to be the dominant criterium

LHC Days 2001 Villars-sur-Ollon, Massimiliano Ferro-Luzzi, CERN/EP FrequencyConsequence category category Catastrophic Major Severe Minor Frequent I I I II Probable I I II III Occasional I II III III Remote II III III IV Improbable III III IV IV Negligible IV IV IV IV Framework: risk classification table max allowable frequency required frequency Legend:I = intolerable risk II = undesirable but tolerable if risk reduction is out of proportion III = tolerable if risk reduction “exceeds” improvement gained IV = negligible risk Roughly, for the VELO, this table means: for any undesired event LHC Downtime  Frequency  days/year

LHC Days 2001 Villars-sur-Ollon, Massimiliano Ferro-Luzzi, CERN/EP Road map 1 st VELO review with LHCApr Submit TDR to LHCC 3 rd VELO review with LHC (production readiness review) Approval of TDR by RB 2 nd VELO review with LHC May 28 Nov 5 Feb xx Feb yy Fabricate prototype 250  m Al shield Test mechanical properties of shield Test vacuum safety devices (crash scenarios) Measure Z // ( ) Build and test full scale CO 2 cooling system Manufacture vacuum tank Full system test: baking demonstration pump-down procedure venting with ultrapure neon motion mechanics etc. (Milestones to be agreed upon in 1 st VELO review, Apr 3&4, 2001) 2 nd VELO presentation to LEMICJan 23 1 st VELO presentation to LEMICFeb Presentation of TDR to LHCC Jul 4

LHC Days 2001 Villars-sur-Ollon, Massimiliano Ferro-Luzzi, CERN/EP Road map Installation of VELO at IP8 Apr Mar 31 Sep 30 Jan 31 Mar 31 Apr 30 Jul 31 Feb LHC octant test Last dipole delivered 2007 Full machine commissioning Single beam First collisions (pilot run) Shutdown Physics run Dec 31Ring closed and cold VELO commissioning, EMC tests, first tracks LHCb commissioning LHCb: run after... (continued)

LHC Days 2001 Villars-sur-Ollon, Massimiliano Ferro-Luzzi, CERN/EP After numerous LHC/LHCb meetings, including two LEMICs, the design of the VELO has matured to a system with –silicon detectors located in a 2 ary vacuum system –thin separation foil (for RF and vacuum) protected by gravity-controlled and electrically controlled safety valves –a 2-phase CO 2 cooling system in 2 ary vacuum –decoupled access to Si detectors from access to 1 ary vacuum system by using ultrapure inert gas venting –possibility to bake out up to T  150 o C –smooth conducting wall throughout setup for mirror charge (study wake field effects by simulations and tests with full scale model) Major integration issues being addressed: dynamic vacuum, electron multipacting, impedance, RF losses, safety Design has now clear support from LHC/VAC (see LEMIC jan/2001 and LHC-TC feb/2001)  “door open” for TDR Summary

LHC Days 2001 Villars-sur-Ollon, Massimiliano Ferro-Luzzi, CERN/EP LHCb/VELO: continue extensive prototyping and testing Mechanism for supervision by LHC was set up: –at least 3 reviews before installation at LHC –risk analysis to assess acceptability (not only LHC-VAC...) –perform all required tests before installation into LHC Further interaction with LHC groups is essential: –vacuum: “sector” valves, more data and simulations needed on dyn. vac. effects, e.g.  i of saturated NEGs, photon flux at IP8, e-multipacting, etc. –choice and configuration of equipment: vacuum pumps, valves, diagnostics equipment, controls (PLCs), etc. (radiation environment) –beam failure scenarios and IP8, radiation monitors, etc. Aim: full system setup with Si detector modules in LHC during single beam operation in feb+mar 2006 Outlook