THIRD LOAN MODIFICATION AGREEMENT
This Third Loan Modification Agreement (this “Loan Modification Agreement’) is entered into as of
November 16, 2006, by and between SILICON VALLEY BANK , a California-chartered bank, with its
principal place of business at 3003 Tasman Drive, Santa Clara, California 95054 and with a loan production
office located at One Newton Executive Park, Suite 200, 2221 Washington Street, Newton, Massachusetts
02462 (“Bank”) and AMERICAN SCIENCE AND ENGINEERING, INC , a Massachusetts corporation
with its chief executive office located at 829 Middlesex Turnpike, Billerica, Massachusetts 01821 (“Borrower”).
1. DESCRIPTION OF EXISTING INDEBTEDNESS AND OBLIGATIONS . Among other
indebtedness and obligations which may be owing by Borrower to Bank, Borrower is indebted to Bank pursuant
to a loan arrangement dated as of August 11, 2003, evidenced by, among other documents, a certain Loan and
Security Agreement dated as of August 11, 2003, between Borrower and Bank, as amended by a certain First
Loan Modification Agreement dated as of June 30, 2004, between Borrower and Bank, and as further amended
by a certain Second Loan Modification Agreement dated as of November 30, 2004, between Borrower and
Bank (as amended, the “Loan Agreement”). Capitalized terms used but not otherwise defined herein shall have
the same meaning as in the Loan Agreement.
2. DESCRIPTION OF COLLATERAL . Repayment of the Obligations is secured by the Collateral as
described in the Loan Agreement and the Intellectual Property Collateral as described in a certain Intellectual
Property Security Agreement dated as of August 11, 2003, as amended by a certain First Amendment to
Intellectual Property Security Agreement dated as of August 23, 2004 (as amended, the “IP Security
Agreement”) (together with any other collateral security granted to Bank, the “Security Documents”).
Hereinafter, the Security Documents, together with all other documents evidencing or securing