Qweak Target Meeting Greg Smith Dave Meekins Mike

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?

15 K standoff Relief Design to ballas tank 300 K sleeve G 10 spacer 4 K standoff 2 7/8” id cold relief 6” od relief bellows (3. 5” id) short flex hose to loop to accommodate horizontal motion (not shown)

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 LN 2 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 LH 2 test winter 2009 -2010 Run for Qweak spring 2010 -2012

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 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 G 0 D 2

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 House Helium Line (300 K Supply) HMS *warm* T 20 K Return Line 15 K, 12 atm supply Hall C Moller 15 K Supply 12 atm Line 20 K Return Line New HX Short New Ins. Line 4 K 3 atm Supply Line 300 K 4 atm supply 20 K, 3 atm return WR Line CHL 4. 5 K 3 atm 4 K, 3 atm supply 5 K, 1 atm return Warm return ESR H 2 Ballast Tank H 2 vent HP HX: LP HX: 20 K 1 atm return 20 K 2. 5 atm Return 20 K, 50 psia LH 2 Loop QW Tgt Qweak Gas Panel Oct. , 2007, GRS

Relief Calculation Strategy • Follow “Hydrogen Safety Assessment Document” written by Mike Seely for the Jlab LH 2/LD 2 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 (1/2 done) 3. Worst case accident: inventory dumps into Hall C

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

Sudden LOV • Assume target cell remains intact – LH 2 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 300 K (worst case) X – Internal plumbing stays at 80 K (worst case is 300 K) X – Superinsulation (worst case is no superinsulation)

Ballast Inventories

More Storage? Existing: 2 2500 gal tanks 1 1000 gal tank Drop Pop Pstorage drops Assumes: • 45 psia Poperating • 52 liters LH 2 • More storage doesn’t really help that much: – Doubling Vstorage only reduces Pstorage ~20% • because Poperating is so high – Puts more gas into hall in event of an accident

Baselining Sudden warmup, Hall C tgt, Nov. 13, 2007: Pstorage ΔP • Observed ΔP=1. 6 psi • Calculated ΔP=2. 6 psi Pressure – Conservative assumptions • Sudden LOV • 300 K external relief lines • 80 K internal relief lines • Observed Δt~5 min • Calculated Δt=2 min Pretty reasonable agreement! Temperature

Qweak Heat xfer Coefficients

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

15 K standoff Relief Design to ballas tank 300 K sleeve G 10 spacer 4 K standoff 2 7/8” id cold relief 6” od relief bellows (3. 5” id) short flex hose to loop to accommodate horizontal motion (not shown)

Qweak LOV ΔP 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 LH 2. Completely reasonable! ~Same as for existing Hall C tgt

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 Case SI Qtot (W) mdot (g/s) Plumbing ΔP (psi) 1 All but windows 1900 4. 6 Existing 1. 4 2 None 28000 68 Existing 292 “ “ 20’ 1” 2” hose 45’ 1” 2” tube 21. 5 “ “ Case 3 + 150’ 2” 75’ 2” (2 existing 150’ 2” lines in ||) 18. 5 “ “ Case 4 + 20’ 2” hose 20’ 3” hose 14. 1 3 4 5 Note: 75 psia storage pressure, 100 psia reliefs on ballast tanks: ΔPmax = 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 G 0 + 1 Hall C tank looks OK – Adding a 3 rd “G 0 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 – LH 2 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* Pmax 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 Dome penetration Vent Stack Eight 4” penetrations to outside

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 LH 2 • 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 H 2 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