1. p2n Converter Geneva Meeting
TRIUMF Report
Geneva, October 16, 2017
Luca Egoriti
Alexander Gottberg
Tom Day Goodacre

2. Content UCx 100 µA license amendment
Past design overview + updated concepts
Target
Converter
p2n offline tests
Future tasks

3. UCx 100 µA License Amendment
Meeting with TRIUMF radiation protection group (Mon, Oct 2nd):
2-step process:
Internal (TRIUMF accelerator division) safety review
CNSC safety approval, ~12 weeks processing time
Proton beam tails could increase α-emitting inventory: to be quantified
Beam tails and halo known and characterized
Now: retrieving data and evaluate impact on radioisotope inventory
Ongoing: benchmarking set limits of halo monitor and discussion with beam physics group for reducing tails
Fr isotopes online production as a benchmark for α-inventory
Schedule
FLUKA inventory simulation and data analysis (Nov 30th)
Internal safety review (December 2017)
Submit application for safety review by TRIUMF EH&S (Jan 2018)

4. Past overview Target

5. Initial Connection, Target Legs, Target Body
Thermal gradients top-down always present in any simulation
Lateral thickness 0.2 mm seemed the only option, but high risk of failure

6. Thermal Optimization Study
Changed current leads geometry
Better temperature distribution
Cold spot in the center without beam interaction
Temperature:
Max on legs = 3500 °C (can be optimized by changing profile)
Max on container = 2700 °C (can be optimized but will lower average temperature)

7. Iterations

8. Latest target – “Smiley heart” target
Tmax [°C]
Tmin [°C]
Legs
2750
1870
Container
2521
1575
Graphite boat
1950
1860
Increases by 200 °C during 50 kW beam irradiation (~30 W deposited in 0.15mm Ta window)
At max converter temperature: container cap is still <2000 °C
Length = 30 mm
Diameter = 40 mm
Lateral thickness = 0.38 mm (TRIUMF targets, sustainable when TaC coated)
Legs: two different thicknesses (2.5 mm; 1.5 mm) before and after splitting
Legs and end-caps EDM out of one single tantalum piece
Machining challenge: 40 mm diameter
3.7 V voltage drop across target (leg to leg)

9. Hot converter scenario
If entire converter surface is at °C:
Radiation from Converter to Target: 430 W
Max T on target cap:
Emissivity 0.2  Tmax=1925 °C
T-dependent emissivity  Tmax = °C
Consequence: target affected positively, T more homogeneous
Next steps:
Optimizing tantalum profile
Experimental verification
Experimental optimization through heat shields

10. Past overview Converter

11. First TRIUMF concept Brings converter close/inside annular UCx
Run converter as moderate in temperature as possible.
copper
tungsten
Parameters
N-induced
9.49 E12 [fiss/sec]
%p-induced fiss
4.65% [(p-ind fiss)/(tot fiss)]
Tot Pow Dep [W]
6659 W
Max Temperature in W
1652 °C
Max Temperature in Cu
638 °C
Graphite boat
Tantalum container and windows
UCx
Clamping issue over beam cycles
Target heating not properly addressed
Target: machining challanging
Ta beam windows machining/assembly not addressed

12. Ta + Cu, Radiation included
Entire converter
Cu only
Water path
Beam Heating = 7730 W
Tmax tungsten = 1800 °C
Tmax copper = 290 °C
Tmax WaterLine = 200°C
Max Cu plastic strain = 0.007
Max W plastic strain =

13. Previous Converter Geometry
Tmax in tungsten ~1860 °C
Tmax in copper ~350 °C
Tmax water pipes ~160 °C
2 cm
7 cm
2 Issues:
Tungsten 6 mm away from Copper surface  lower solid angle for neutrons to UCx
Two contact surfaces: different thermal contact due to machining tolerances

14. Latest converter - Geometry
6mm
10mm
4mm
p-beam
14 mm
13mm
Tungsten in line with copper – minimizes distance W-UCx
Minimizes distance W-UCx
Asymmetries in Copper: more thermal mass in the rear one  can take more power
Tungsten asymmetry to distribute power differently front-rear
Additionally, front one takes ~300 W thermal radiation from target
Run thermal-electric on target only, computed radiation power from front surfaces
Applied temperature boundary condition so that emits the same power, run thermal simulation on the entire geometry to assess converter temperature
Assumption: copper emissivity/”absorptivity“ = 0.1, while polished copper <0.07 (conservative, if stays polished)
1 mm distance between copper brackets
Different copper bracket thickness to distribute heat flow more evenly over the pipe cooling interface
Copper fillets

15. Latest Converter – Simulation Results
Different Tmax in the two copper brackets
Tmax (tungsten) = 2137 °C
Different Tmax in the two cooling lines [Tmax (front)=140°C; Tmax (rear)=180 °C]
Water temperature from simulations = 60 °C  colder water could go first in the rear bracket to avoid boiling [Tsat bar) ~165 °C]
Tmax1 = 385 C
Tmax2 = 361 C
Comparison with previous simulation: W symmetrical, Cu asymmetrical
Tmax (W) = 2250 °C
Tmax (Cu) = 440 °C

16. Test Stand Target

17. p2n Target Heating Tests in ATTS
Two optical lines of sight for pyrometer (P) measurements
4 K-type and 4 C-type thermocouples
First p2n target machined with AETE material
Tests to be fitted in AETE-target test schedule
Schedule
ATTS modifications available to fit p2n target tests: (Fri, Nov 10th)
First target machined with AETE material (Thu, Nov 30th)
First full heated test with 1500A (Christmas 2017)
Tests to be fitted in AETE-target test schedule
(P)
(P)
Test aim
Benchmark simulations with pyrometer temperature data
Prove target integrity after 1 cycle
Prove target integrity for long continuous operation (ideally 3 weeks)

18. Implementation Heat balance: Ohmic heating (1500 A; 3.7 V) = 5550 W
Beam power deposition = 7300 W
Total power deposited = W
Max allowed power deposition = 12 kW
→ More simulation and validation work required
Power supplies proposal:
Three parallel power supplies (600 A; 16V)
Short them while entering two power lines (target heater + FEBIAD magnet coil)
Distribute current evenly until they are merged together at the connectors
AC/DC transformer station to be checked with Franco
Target + Converter mass
I talked to Franco via to arrange a meeting this past week, he seemed into it but I still haven’t got any reply after I sent 2 reminders. Will tackle him in person next week.

19. Test Stand Converter

20. p2n Converter Test Stand 1
Thermocouple- out (water)
Thermocouple- in (water)
Similar geometry to the online converter
Contact temperatures much lower than online converter
Table-top: converter and TIG welder hold in place with equipment present in Remote Handling shop
Thermocouples attached with wire
Power: 1000 W
Cooling: 1000 [W/m2 K]
central TC= °C
lateral TC = 80 °C
Thermocouple holes
Argon flow to prevent oxidation
TC1 = 70°C
TC2 = 67°C
TIG welder tip
TIG welder ceramic support

21. p2n Converter Test Stand 2 – Asymmetric (new proposal)
Scenario
h[W m^-2 C^-1]
Power [W]
Tmin W [°C]
Tmax W [°C]
Tmin Cu [°C]
Tmax Cu [°C] 1
1000
750
337.6
2051.1
147.8
535.1 2
2000
263.1
1976.4
78.8
460.2 3
4000
224.4
1937.5
47.7
421.3 4
6000
210.6
1923.7
39.0
407.6 5
500
235.1
1377.4
108.5
366.7 6
185.4
1327.6
62.5
316.8 7
159.6
1301.7
41.8
290.9 8
150.4
1292.5
36.0
281.7

22. p2n Converter Test Stand - Schedule
Fri, Oct 29th: Standard copper pieces ready
Mon, Nov 13th: Joao Pedro arrives at TRIUMF with W piece(s)
Wed, Nov 15th: Copper brackets + W converter(s) assembled by TRIUMF machine shop
Thu, Nov 16th: Setup and troubleshooting
Fri, Nov 17th – Tue, Nov 24th:
Copper conductance + thermal cycling tests:
Ramp-up 0  1000W in ~10 mins
Ramp down 1000W  0 W in ~10 mins
As many cycles as possible in the
Deformation/damage assessment on Cu and W
All W parts duplicated for future CuCrZr tests if needed
(CuCrZr has yield stress higher than copper by a factor 100)
Kth copper
Kth CuCrZr

23. Future tasks Cooling system Max outlet temperature:
Heat exchanger (rated for 120 kW for the whole system) could be enough
Plastic pipes limit water temperature. Check for changing material/replacement frequency
Pressure drops calculation: additional heat shield pipes + converter water path might affect too much water flow
Write EEC proposal (Start now)
ISAC infrastructure
Check for AC/DC conversion capabilities (Franco). Fri, Oct 20th
Order 2 (600 A, 16V) power supplies in parallel to the same already existing one (Nov, 15th)
Simulate thermal load to the target and FEBIAD connectors
ISAC test stand: (Dec 2017)
Water-cooled connector test up to 1000 A
Temperature measurement (previous thermocouple implementation)
ISAC target module connector test (During shutdown, Jan-Apr 2018)
Water-cooled connector test up to ~1800 A
Thermocouple implementation)
On average, there is a 3-month mismatch between initial test plan and current situation

24. Suggested Geometry
Only one step because of potential bad/no contact while expanding and because of machining tolerances