Exhibit 10.15

FIRST AMENDMENT TO SUBLEASE,

SUBORDINATION, NON-DISTURBANCE AND ATTORNMENT AGREEMENT

THIS FIRST AMENDMENT TO SUBLEASE, SUBORDINATION, NON-DISTURBANCE AND ATTORNMENT AGREEMENT (this “Agreement” ), dated for reference purposes only as of April 2, 1999, is made by and among VARIAN, INC., a Delaware corporation ( “Sublessor” ), COMMUNICATIONS & POWER INDUSTRIES, INC., a Delaware corporation ( “Sublessee” ), VARIAN ASSOCIATES, INC., a Delaware corporation ( “Varian Associates” ), and VARIAN REALTY INC., a California corporation ( “Varian Realty” ). Varian Associates and Varian Realty are sometimes hereinafter collectively referred to as “Ground Lessee” .

Recitals:

A.                                   Varian Associates, a California corporation ( “Varian California” ), and The Board of Trustees of the Leland Stanford Junior University ( “Stanford” ) are the parties to that certain unrecorded Lease dated July 1, 1959, as subsequently amended by Varian California and Stanford (the “Original Lease for Units 6, 7, 10 and 12” ), whereby Varian California leased from Stanford certain real property located in Palo Alto, California, commonly referred to as Units 6, 7, 10 and 12.

B.                                     Varian California and Stanford are the parties to that certain unrecorded Lease dated January 1, 1956, a Memorandum of Lease having been recorded June 25, 1956, in Book 3532, at Page 469, Records of Santa Clara County, California, as subsequently amended by Varian California and Stanford (collectively, the “Original Lease for Units 5 and 11A” ), whereby Varian California, leased from Stanford certain real property located in Palo Alto, California, commonly referred to as Units 5 and 11A. The Original Lease for Units 6, 7, 10 and 12 and the Original Lease for Units 5 and 11A are collectively referred to herein as the “Original Leases” .

C.                                     Varian Associates, as the successor to Varian California as the “Lessee” under the Original Lease for Units 6, 7, 10 and 12, as “Sublessor”, and Sublessee, as “Sublessee” entered into that certain Sublease (Building 4, Palo Alto) dated August 10, 1995, a Memorandum of Sublease (Building 4, Palo Alto) having been recorded August 10, 1995, as Instrument No. 12979123, Records of Santa Clara County, California (collectively, the “CPI Sublease” ), whereby Sublessee subleased from Varian Associates a portion of the building situated on Unit 6, located at 3120 Hansen Way, Palo Alto, California, and commonly referred to as Building 4 ( “Building 4” ). The CPI Sublease is subject and subordinate to the Original Lease for Units 6, 7, 10 and 12.

D.                                    Varian Associates and Stanford separated the Original Lease for Units 6, 7, 10 and 12 into three separate leaseholds, and Varian Associates,

1

Varian Realty and Stanford combined the leaseholds for Units 5, 6 and 11 A in to a single lease pursuant to that certain Restated and Amended Lease by and between Varian Associates and Varian Realty, collectively as “Lessee”, and Stanford, as “Lessor”, dated March 30, 1999, a Memorandum of Restatement and Amendment of Lease having been recorded March 30, 1999, as Instrument No. 14729331, Records of Santa Clara County, California (collectively, the “Restated and Amended Lease” ).  The Restated and Amended Lease restates and amends the Original Leases with respect to Units 5, 6 and 11A.

E.                                       Varian Associates and Varian Realty, collectively as “Sublessor”, and Sublessor, as “Sublessee”, have entered into that certain unrecorded Sublease dated as of April 1, 1999 (the “Varian, Inc. Sublease” ), whereby Varian Associates and Varian Realty subleased to Sublessor all of Building 4 and the adjacent back yard fronting on Hanover Street.

F.                                     The interest of Varian Associates and Varian Realty in and to the CPI Sublease was assigned to Sublessor pursuant to that certain unrecorded Assignment and Assumption of Sublessor’s Interest in Subleases dated April 2, 1999 by and between Varian Associates and Varian Realty, collectively as “Assignor”, and Sublessor, as “Assignee” (the “Assignment” ). A copy of the Assignment is attached to this Agreement as Schedule 1 .

G.                                    Sublessor and Sublessee desire to (1) amend the CPI Sublease to reflect the restatement and amendment of the Original Leases for Units 5, 6 and 11A by the Restated and Amended Lease; (2) subordinate the CPI Sublease to the Varian, Inc. Sublease; and (3) provide for the attornment of Sublessee to Sublessor; and Sublessee desires to obtain from Ground Lessee non-disturbance protection in the event of the termination of the Varian, Inc. Sublease, all as set out in this Agreement.

Agreements :

NOW, THEREFORE, in consideration of the agreements of Sublessor, Sublessee and Ground Lessee set forth in this Agreement and other good and valuable consideration, the receipt and adequacy of which is hereby acknowledged, Sublessor, Sublessee and Ground Lessee agree as follows:

1.                                        Amendment of the CPI Sublease . Sublessor and Sublessee hereby amend the CPI Sublease as follows:

a.                                        Adjacent Property Lease . The definition of “Adjacent Property Lease” set out in Section 1.1 of the CPI Sublease is hereby deleted.

b.                                       Adjacent Property Sublease . The definition of “Adjacent Property Sublease” set out in Section 1.1 of the CPI Sublease is hereby deleted.

2

c.                                        Master Lease . The definition of “Master Lease” set out in Section 1.1 of the CPI Sublease is hereby amended to read in its entirety as follows:

“Master Lease” means that certain Lease, dated July 1, 1959, by and between Stanford, as lessor, and Varian Associates, a California corporation, as lessee, for the lease of real property and improvements (“Unit 6 Premises”), as such Lease has been restated and amended pursuant to that certain Restated and Amended Lease dated March 30, 1999, by and between Stanford, as lessor, and Varian Associates, Inc., a Delaware corporation, and Varian Realty Inc., a California corporation, collectively as lessee, a Memorandum of Restatement and Amendment of Lease having been recorded on March 30, 1999, as Instrument No. 14729331, Records of Santa Clara County, California, together with such rules, regulations and guidelines as Stanford may adopt from time to time. A copy of the Restated and Amended Lease is attached hereto as Exhibit F and incorporated herein by this reference.

From and after the date of this Agreement, all references contained in the CPI Sublease to the “Master Lease” shall be deemed to refer to the Restated and Amended Lease.

d.                                       Premises . The definition of “Premises” set out in Section 1.1 of the CPI Sublease is hereby deleted.

e.                                        Sublessor . The definition of “Sublessor” set out in Section 1.1 of the CPI Sublease is hereby amended to read in its entirety as follows:

“Sublessor” means Varian, Inc., a Delaware corporation.

From and after the date of this Agreement, all references contained in the CPI Sublease to “Sublessor” shall be deemed to refer to Varian, Inc., a Delaware corporation.

f.                                          Exhibit B . Exhibit B attached to the CPI Sublease is hereby replaced with the diagram attached to this Agreement as Exhibit B . From and after the date of this Agreement, all references contained in the CPI Sublease to Exhibit B or to the “Unit 6 Premises” shall be deemed to refer to Exhibit B attac