Qweak Target Meeting Greg Smith, Dave Meekins, Mike Seely, Silviu Covrig January, 2008 Design Questions Signals/Feedthrus Relief Stack Job Jars Schedule Safety/Relief Calculations

Top Plate Design Questions –Coolant standoffs Length “cut to fit” by tgt grp Interferences? Accessibility? Relative height? Several sizes in use at Jlab, Bert needs your guidance here –Lifter EC position fixed –Electrical feedthrus Bert needs input asap (part goes out this week) How many of what type? HPH feedthru config (2 or 2*4?) Spares

Top Plate Layout

Coolant Standoffs

Target Signals

Electrical Feedthroughs

Relief Plumbing Questions –Fill line and separate return line Opposite sides of pump –Mike suggests very small fill line, has to go on suction side of pump Coaxial (sort of) to main 2 7/8 ” id vent –Ok? Thermal crosstalk a problem? ½” fill line. OK? Bigger? With a gusset. –Pump geometry fixed to opposite leg as relief line. Means return line attaches to upper corner opposite pump, on output side of pump –So can’t ever use this to fill the target! –Pump differential pressure relative to ½” fill line –Fill & return mainly tube, with short hose Heater tape? –Separate tap for vapor pressure bulb? Coaxial too?

Relief Design 6” od relief bellows (3.5” id) 2 7/8 ” id cold relief G10 spacer 300K sleeve short flex hose to loop to accommodate horizontal motion (not shown) to ballast tank 4K stand- off 15K stand- off

Coaxial Fill Line Fill: ½” Return: 2 7/8 ” id

Up & Down Fill: ½” Return: 2 7/8 ” id

Broken Symmetry Given: Pump must be on opposite side as relief stack. Fill line must be on inlet side of pump. Heater will be on the leg opposite to the HX. Question: Which side of pump should HX be on? Suction side, as shown here? Or the other side?

Coarse Schedule Safety Review this spring Test pump in LN2 late spring –Must decide if we need to go commercial by August Assemble tgt this summer Test tgt this fall in test lab with GHe Neon test spring 2009 Install in Hall C fall 2009 LH2 test winter Run for Qweak spring

Bert’s Design Job Jar –Transition between 2 scattering chambers Needs pump, HX geometry (fixes ht) –SC window Needed for Safety review? –SC ports Where? How many? –Motion mech’s –Relief stack –Cryostacks –New relief/vent plumbing –Top plate Needs feedthru info –8” SS pipe –Bracket that fixes the loop to the 8” pipe –Loop basics –Qweak Support/Storage tripod –Support plate HKS stand to SC –Gas Panel schematic

Target Group Design Job Jar (with some help from GRS, SDC) –Cell –Cell manifolds –Cell positioner –Exit window >7” diam,.005” nipple –Entrance window –Pump –HX –Dummy target/ladder design? Bert/Dan? –Gas Panel Hall C techs? GRS/SDC –Loop details –Survey tools –Help on safety document –Dump G0 D2

The Fast Track Motion Mechanisms built by March Relief stack & top plate built by March Tripod by March Pump prototype –Build early spring, test by late spring Need 1 year if we have to go to BN HX could be ready in 3 weeks... Cell mechanical design by spring –Fabricate late spring/early summer Heater by summer (MSU) Gas panel by summer SC ready by fall –Transition, ports

The Slow Track Plate for HKS stand/Sample SC transition SC window (a big job) Cell positioner –Need a wag though New Relief & Vent plumbing Final exit & entrance windows –Need something though (could be thick) Ballast tanks New HX from cryo Dummies New HX for CHL return from cryo group

Dirty gas to CHL HP HX: 20 K 1 atm return 15K, 12 atm supply T CHL 4.5K 3 atm Q W Tgt Hall C New HX ESR Oct., 2007, GRS Short New Ins. Line 20K Return Line WR Line 15K Supply 12 atm Line 20K Return Line House Helium Line (300K Supply) 20K, 50 psia LH2 Loop 20K, 3 atm return 300K 4 atm supply 5K, 1 atm return 4K, 3 atm supply Hall C Moller HMS *warm* Qweak Gas Panel H2 Ballast Tank H2 vent LP HX: 20 K 2.5 atm Return Warm return 4K 3 atm Supply Line

Relief Calculation Strategy Follow “Hydrogen Safety Assessment Document” written by Mike Seely for the Jlab LH2/LD2 targets in 2004 Reproduce those calculations: –Get Mike Seely to agree with results –Compare to actual performance Use the resulting tested and certified template to design & calculate Qweak relief in 3 scenarios: 1.Design for a sudden LOV incident 2.Design for a cell rupture 3.Worst case accident: inventory dumps into Hall C (1/2 done)

Basic Relief Ballast Tank Relief Line Outside World Inside Hall C Outside Vent 3) Cell & Window Rupture into Hall C Scattering Chamber 2) Cell Rupture 1) LOV, No Ruptures

Sudden LOV Assume target cell remains intact –LH2 boils rapidly and relieves to ballast tank –No gas gets into vent header (relief valves remain closed) Can occur if: –A scattering chamber window breaks –A pump fails –A valve to atmosphere inadvertently opened Will be deliberately tested (with Neon) Want to calculate: Maximum pressure rise Assumptions: –External plumbing is 300K (worst case) –Internal plumbing stays at 80K (worst case is 300K) –Superinsulation (worst case is no superinsulation) X X

Ballast Inventories

More Storage? Assumes: 45 psia P operating 52 liters LH 2 Drop P op  P storage drops More storage doesn’t really help that much: –Doubling V storage only reduces P storage ~20% because P operating is so high –Puts more gas into hall in event of an accident Existing: gal tanks gal tank

Baselining Sudden warmup, Hall C tgt, Nov. 13, 2007: Pressure Temperature Observed ΔP=1.6 psi Calculated ΔP=2.6 psi –Conservative assumptions Sudden LOV 300K external relief lines 80K internal relief lines Observed Δt~5 min Calculated Δt=2 min ΔPΔP P storage Pretty reasonable agreement!

Qweak Heat xfer Coefficients

Heat Load from Heat Flux and Area Not that different from the Hall C standard pivot target!

Relief Design 6” od relief bellows (3.5” id) 2 7/8 ” id cold relief G10 spacer 300K sleeve short flex hose to loop to accommodate horizontal motion (not shown) to ballast tank 4K stand- off 15K stand- off

Qweak LOV ΔP Completely reasonable! ~Same as for existing Hall C tgt With the plumbing that exists in the Hall right now. Using existing ballast tanks. 45 psia operating P. Superinsulation on loop except at windows. 52 liters LH2.

Relief Path Question: relief lines have a goofy bottleneck where they connect to the ballast tank: looks like 2” to 1” to 2”.

Sudden LOV Results CaseSIQ tot (W) mdot (g/s)Plumbing ΔP (psi) 1All but windows Existing1.4 2None Existing292 3 ““ 20’ 1”  2” hose 45’ 1”  2” tube ““ Case ’ 2”  75’ 2” (2 existing 150’ 2” lines in ||) ““ Case ’ 2” hose  20’ 3” hose 14.1 Note: 75 psia storage pressure, 100 psia reliefs on ballast tanks:  ΔP max = 25 psi Conclusion: With minor mods to existing Hall C plumbing, we can withstand a sudden LOV even if all SI is blown away!

Relief Plumbing Tie into existing 2” relief lines to ballast tank here, with 40’ of new 2” line to the Qweak target (replacing existing 1” lines).

Sudden LOV Summary Ballast: 2 G0 + 1 Hall C tank looks OK –Adding a 3rd “G0 tank” may be desirable To handle most realistic case, do not need to do anything To handle worst case, need to: –Replace 1 st 20’ of 1” hose with 2” or 3” hose –Replace next 45’ of 1” tube with 2” tube –Put both 150’ 2” lines back to tanks in ||

Cell Rupture Assume target cell ruptures –LH2 inventory dumps into scattering chamber Scattering chamber windows remain intact –It boils rapidly and expands Must handle entire gas inventory until ballast tank reaches 1 atm Reality: not hard to keep ballast gas outside hall Can occur if: –Relief line back to ballast tank becomes blocked –Structural failure of cell Will not be directly tested, –but all components must be tested to 1.5* P max expected in a sudden LOV incident Want to calculate: Scattering Chamber ΔP –Note: no downstream beamline gate valve

Qweak cell rupture Need some extra (beam pipe) volume to slow it down. (we have it: no gate valve!)

Heat xfer rate Function of the scattering chamber geometry (and initial conditions) Still have to include heat transferred to gas from beam pipe volume. Makes things worse.

Result Existing!

Vent Path Scatt. Chmbr vents thru burst disk & relief valve in || Can use same plumbing for Qweak 2” vent line

Vent Path Existing 2” Vent Line Eight 4” penetrations to outside Dome penetration Vent Stack

Cell Rupture Results Must add some beam pipe volume –Allows liquid to boil away without increasing pressure inside scattering chamber –No space for a downstream gate valve anyway Calculation assumes 52 liters LH2 Existing 2” vent plumbing is adequate! –More penetrations are available SC ΔP(Qweak) < ΔP(Standard Hall C tgt) Caveat: have not treated beam pipe volume yet... –Additional dump volumes possible in principle

Worst Case Accident Simultaneous failure of Scattering Chamber windows AND Cell rupture –Very unlikely, but Projectile from outside could penetrate both in principle Cell rupture could potentially puncture SC windows –Have to assume H2 inventory gets into Hall C until ballast tank reaches 1 atm –Even though this can be prevented with good design

More on Gas Inventories

Options in worst case scenario Let it go (current solution): –no roof on tgt shield cave –vacuum interlock top plate electronics lifter, heater, JTs, etc. –rely on Hall volume, dome vent Or, in addition (cuz of P wave problem): –Provide large vent hood over tgt top plate –“dryer plumbing” to 2’ φ Hall penetration –possibly also kick (explosion proof) vent fan on with vacuum interlock

Finished