Page 1 Thinning of stamped End cap 1.The measurement from Niowave shows the corners of FPC and H-HOM openings are thinned and its thinnest area is 2.2mm. 2.The thinning occurs at the corners only. 3.The initial stress study was done with 3.5mm thick body when we were asked to look into 6mm stiffener instead of 8mm. 4.The stress profile of 3.5mm thick cavity shows low stress on the straight area of the wave guide stub → possibility of allowing the thinning 5.Making a model of various thickness is time consuming. Instead, 2.2mm and 2.8mm uniformly thick cavity were modeled and the local stress was checked. 6.Niobium room temperature property, E=1E+11 Pa, PR=0.4

Measurements 2

3 Highest Thinning Region

Page 4 High Stress Locations Red is above 50 MPa. This slide is from the presentation last year. 3.5mm thick Nb provides enough strength all over the cavity except the stiffer area. The VHOM opening area needs to be carefully looked if the material gets thinner.

Page 5 Stress check method 1.Model thinner cavities, 2.2mm and 2.8mm uniform. 2.Stress is calculated with the whole cavity. 3.Make a cross section where the opening is machined. 4.Check the corresponding local stress. Cross section at 7mm above 3.5mm thick stress profile Machined area Thinner cavity stress profile 3.5mm thick cavity shows stress is mostly on the curved surface and these area is much thicker than 3.5mm.

Page 6 2.2mm thick cavity-check inner corners New B1 B2 T1 T2

Page 7 2.2mm thick cavity B1 T1 T1 corner has above 50MPa area but the bulk is MPa. Linearized stress is fine.

Page 8 2.8mm thick cavity-check outer corners Entire bulk is below 50MPa.

Page 9 The other end cap? The same thinning trend is anticipated with the other end cap. Inner corner thinned to 2.2mm and outer corner 2.8mm. 2.2mm outer corners are OK. Disregard these area Disregard these numbers. It’s from the other side.

Page mm outer corners of VHOM opening The first look requires the stress linearization. 3 paths were checked.

Page 11 Stress linearization-worst path Membrane stress 35 MPa, less than 50 MPa allowable Total stress 68 MPa, less than 75 MPa allowable

Page 12 Conclusion 1.The local thinning is at the low stress area and it won’t compromise the mechanical strength of the cavity. 2.VHOM side end cap was checked assuming the thinning effect. 3.The study shows the stamped end cap meets the stress requirement. We recommend Niowave to proceed and stamp the other side.